Fuel container

ABSTRACT

A fuel container with high fuel barrier properties is provided. The fuel container is a coextrusion blow-molded container made of a layered structure. The layered structure comprises: a barrier layer made of a barrier resin (A) and an inner layer located on an inner side of the container with respect to the barrier layer, the inner layer being made of a thermoplastic resin (B) that is different from the barrier resin (A); wherein the container has a pinch-off part formed in a process of blow molding of a parison made of the layer structure, and wherein the pinch-off part has a cutting face comprising a cutting face of the barrier layer and a cutting face of the inner layer; and wherein the cutting face of the inner layer is covered by a barrier member made of a barrier material (C) that is the same or different from the barrier resin (A).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel container having high gasolinebarrier properties.

2. Description of the Related Art

In recent years, coextrusion blow-molded containers made of plasticmaterials are preferably used for containers for storing fuels, such asgasoline, and examples for such containers are the fuel tanks of motorvehicles. As for the plastic material used as the material of suchcontainers, there are high expectations in polyethylene (especially veryhigh-density polyethylene) with regard to economic efficiency, moldingprocessability, mechanical strength, and the like. However, it is knownthat fuel tanks made of polyethylene have a disadvantage that the storedliquid gasoline and/or the vaporized gasoline easily permeates throughthe polyethylene walls into the atmosphere.

To eliminate this disadvantage, a method is known in which a halogen gas(e.g. fluorine, chlorine, or bromine) or sulfur trioxide (SO₃) or thelike is blown into the polyethylene container, and the inner wall of thecontainer is halogenized or sulfonated. Another method that is known isto obtain a container that has a multilayered structure and is made of apolyamide resin layer and a polyethylene resin layer (see JapaneseLaid-Open Patent Publication No.6-134947, U.S. Pat. No. 5,441,781). Yetanother method that is known is to obtain a container that has amultilayered structure and is made of an ethylene-vinyl alcoholcopolymer (EVOH) resin layer and a polyethylene resin layer (see U.S.Pat. No. 5,849,376 and EP 759359). Furthermore, a fuel tank is known,which has a multilayered structure and includes an inner layer, an outerlayer, and a layer with gasoline barrier properties (i.e., a barrierlayer), and in order to enhance the gasoline barrier properties, thebarrier layer is arranged closer to the inner layer (see JapaneseLaid-Open Patent Publication No.9-29904 and EP 742096).

However, in the manufacture of fuel containers according to thesemethods, the gasoline permeation amount cannot be suppressedsufficiently. Recently, there are strong demands with respect to theeconomic consumption of gasoline and the protection of the environment,and there is a strong demand for the reduction of the gasolinepermeation amount in fuel containers.

SUMMARY OF THE INVENTION

A first fuel container of the present invention is a coextrusionblow-molded fuel container having a container body made of a layeredstructure, the layered structure comprising: a barrier layer made of abarrier resin (A); and an inner layer and an outer layer made of athermoplastic resin (B) that is different from the barrier resin (A);wherein a ratio (X/Y) of a distance (X) between end portions of thebarrier layer at a pinch-off part of the fuel container and an averagethickness (Y) of the container body is at least {fraction (1/10000)} andat most {fraction (1/10)}; and wherein a ratio (Y1/Y) between a totalthickness (Y1) of the layers of the container body that are located onthe inside with respect to the barrier layer and an average thickness(Y) of the container body is at least {fraction (3/10)} and at most{fraction (7/10)}.

In a preferred embodiment, a ratio H/L between a height H of thepinch-off part and a width L of the pinch-off part of the container is0.1 to 3.

In a preferred embodiment, a MFR (MFRbarrier) of the barrier resin (A)and a MFR (MFRinside) of a resin constituting an innermost layer of thecontainer satisfy the following relation:

8≦MFRbarrier/MFRinside≦100  (1)

wherein MFRbarrier and MFRinside denote values measured at 190° C. undera load of 2160 g, and if the melting point of the resin is about 190° C.or higher, then the measurement is carried out under a load of 2160 g ata plurality of temperatures above the melting point, inverses of theabsolute temperatures are marked on the horizontal axis and thelogarithm of the MFR is plotted on the vertical axis in asemi-logarithmic graph, and the MFR is determined by extrapolation to190° C.

A second fuel container of the present invention is a coextrusionblow-molded fuel container made of a layered structure, the layeredstructure at least comprising: a barrier layer made of a barrier resin(A); and an inner layer made of a thermoplastic resin (B) that isdifferent from the barrier resin (A); wherein a cutting face of apinch-off part of the container is covered by a barrier member made of abarrier material (C).

A third fuel container of the present invention is a fuel container madeof a layered structure, the layered structure at least comprising: abarrier layer made of a barrier resin (A); and an outer layer made of athermoplastic resin (B) that is different from the barrier resin (A);wherein the fuel container is provided with an opening through its body,wherein a cutting face of a layer at the opening is covered by a barriermember made of a barrier material (C), and wherein the layer covered bythe barrier member is located on the outside with respect to the barrierlayer.

A fourth fuel container of the present invention is a fuel containermade of a layered structure, the layered structure at least comprising:a barrier layer made of a barrier resin (A); and an outer layer made ofa thermoplastic resin (B) that is different from the barrier resin (A);wherein the fuel container is provided with an opening, a cut-out or agroove is provided at an outer surface of the fuel container around theopening, and the cut-out or the groove is covered or filled with abarrier member made of a barrier material (C).

In a preferred embodiment of the third and fourth fuel container, apinch-off part of the fuel container is covered with a barrier member.

In a preferred embodiment of the third and fourth fuel container, acomponent for fuel containers is mounted onto the opening portion.

In a preferred embodiment, the component for fuel containers is abarrier member made of the barrier material (C), and the cut-out orgroove is covered by attaching the component for fuel containers.

In a preferred embodiment, the cut-out or groove provided in the outersurface around the opening completely surrounds the opening.

In a preferred embodiment, a depth of the cut-out or groove is 0.1 to0.8 times an average thickness (Y) of the container body.

In a preferred embodiment, a depth of the cut-out or groove is at least0.2 and less than 1 times a total thickness (Y2) of layers locating onthe outside with respect to the barrier layer.

In a preferred embodiment, a width of the cut-out or groove is 0.01 to 5times an average thickness (Y) of the container body.

In a preferred embodiment, a ratio (Y2/Y) of total thickness (Y2) oflayers located on the outside with respect to the barrier layer and theaverage thickness (Y) of the container body is at most {fraction(45/100)}.

In a preferred embodiment, the barrier member covers the cutting face,cut-out or groove via an adhesive.

In a preferred embodiment, a gasoline permeation amount (measured at 40°C. and 65% RH) of the barrier material (C) is at most 0.1 times agasoline permeation amount (measured at 40° C. and 65% RH) of thethermoplastic resin (B).

In a preferred embodiment, a gasoline permeation amount (measured at 40°C. and 65% RH) of the barrier material (C) is at most 400 g·20μm/m²·day.

In a preferred embodiment, the barrier material (C) is at least oneselected from the group consisting of metal foil, epoxy resin,polyvinylidene chloride resin, polyvinylalcohol resin, polyamide resin,polyester resin, and fluorocarbon resin.

In a preferred embodiment of the second to fourth containers, thecontainer comprises: an intermediate layer serving as the barrier layer;and an inner layer and an outer layer made of the thermoplastic resin(B).

In a preferred embodiment, an adhesive resin layer is located betweenthe barrier layer and the layer made of the thermoplastic resin (B).

In a preferred embodiment, the fuel container comprises at least onerecovered layer.

In a preferred embodiment, a gasoline permeation amount (measured at 40°C. and 65% RH) of the barrier resin (A) is at most 100 g·20 μm/m²·day.

In a preferred embodiment, the barrier resin (A) is at least oneselected from the group consisting of polyvinyl alcohol resins,polyamides, and aliphatic polyketones.

In a preferred embodiment, the thermoplastic resin (B) is a polyolefin.

In a preferred embodiment, the thermoplastic resin (B) is high-densitypolyethylene.

Therefore, the present invention described herein makes possible theobjectives of: providing a fuel container having high barrier propertieswith respect to the fuel, for example gasoline, contained in thecontainer; providing a blow-molded fuel container which sufficientlysuppresses fuel permeation at a pinch-off part of the container, and inwhich the pinch-off part has sufficient contact strength, resulting inan excellent impact resistance; and providing a fuel container thateffectively suppresses the fuel permeation at a bonding portion at whicha component is attached to the container.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the pinch-off part of a coextrusionblow-molded fuel container in an embodiment of the present invention;

FIG. 2 is a schematic view showing the pinch-off part of a coextrusionblow-molded fuel container that is not an embodiment of the presentinvention;

FIG. 3 is a schematic view showing the pinch-off part of anothercoextrusion blow-molded fuel container that is not an embodiment of thepresent invention;

FIGS. 4a to 4 d are schematic views showing the shape of pinch-off partforming sections of molds used for examples and comparative examples ofthe present invention (left column), and the shapes of the pinch-offparts of coextrusion blow-molded containers obtained with these molds(right column);

FIG. 5 is a schematic view of an embodiment, in which a component forfuel containers is mounted on an opening provided in the body of thefuel container;

FIG. 6 is a schematic view of an embodiment, in which a barrier membercovers a cutting face of the pinch-off part of the fuel container;

FIG. 7 is a schematic view showing an opening in the body of the fuelcontainer, in which the cutting face of the layer located on the outsidewith respect to the barrier layer is covered with a barrier member;

FIG. 8a and FIG. 8b illustrate the steps for covering the cutting faceof the opening in the body of the fuel container with a barrier member;

FIG. 9a and FIG. 9b illustrate the steps for mounting a barrier memberserving as a component for fuel containers on a cutout that is providedby cutting away a periphery of the opening in the body of the fuelcontainer;

FIG. 10a, FIG. 10b and FIG. 10c illustrate the steps for filling agroove provided around the opening in the body of the fuel containerwith a barrier material (C), and mounting a component for fuelcontainers;

FIG. 11a is a schematic view showing the shape of the barrier memberprepared in Example 11 and FIG. 11b is a cross-section showing anopening of the body of the fuel container on which the barrier member ismounted;

FIG. 12a is a schematic view showing the shape of the barrier memberprepared in Example 12 and FIG. 12b is a cross-section showing anopening of the body of the fuel container on which the barrier member ismounted;

FIGS. 13A and 13B are a schematic view illustrating the steps forforming a cutout that is concentric with the opening in the multilayeredtank, and mounting a barrier member onto this cutout in Example 13; and

FIG. 14 is a schematic view showing an opening in the body of the fuelcontainer on which the barrier member prepared in Comparative Example 15is mounted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As has been mentioned in the above-noted description of the related art,the inventors have performed extensive research to develop a fuelcontainer with high fuel barrier properties.

As a result of this research, the inventors have found that thepermeation of fuel from the container is particularly large at theportion of the pinch-off formed during the molding of the container, andalso that the amount of fuel permeating through portions wherecomponents are attached to the container is too large to be ignored. Asa result of concerted research efforts based on these insights, whichthe inventors were the first to ascertain, the inventors succeeded indeveloping a container having extra-ordinarily high fuel barrierproperties, and thus accomplished the present invention.

The following is an explanation of the permeation of fuel at a pinch-offpart and a portion where a component for fuel containers is attached,which led to the present invention.

Ordinarily, plastic fuel containers are made by blow-molding. For themanufacture of plastic containers by blow-molding, usually a parison ismade by melt extrusion, the parison is held between a pair of molds forblow molding, and then, the parison is pinched off and the pinched offportion is fused at the same time. Then, the pinched-off parisons areformed into the shape of a container by expanding them inside theafore-mentioned molds. However, for large containers, such as vehiclefuel tanks, the parison is held and heat press-sealed, but not pinchedoff with the molds, and the heat-press portion that sticks out from thecontainer surface is mostly cut off with a cutter at the desired height.

The afore-mentioned portion that is coupled by fusing is the pinch-offpart. The pinch-off part forms a protruding line that tapers off in thethickness direction of the container wall. Usually, when an ordinaryparison of a single layer of melted resin is pinched off, the parisoncan be sufficiently coupled at the pinched off portion. Consequently,there is only a low tendency to delaminate at the pinch-off part (whichis the fused and coupled portion) and a low tendency of defectivecoupling, and in practice, containers with sufficient contact strengthcan be obtained. However, with single layers of polyethylene or thelike, the resulting containers have poor fuel barrier properties. If thecontainer is made with a single layer of a resin with high barrierproperties, such as EVOH, then its impact resistance and moldability areinsufficient, and there are disadvantages with regard to cost.

Therefore, such a fuel container is ordinarily produced from amultilayered structure by melt extrusion molding using several kinds ofresins, including a resin with high barrier properties. The gasolinebarrier properties of such a fuel container using the multilayeredstructure including a barrier layer are much better than those in aconventional fuel container using only polyethylene. However, in recentyears, the demands on the gasoline barrier properties of plastic fuelcontainers have become even higher, and there is a strong demand forfurther improvement.

As a result of diligent research, the inventors were the first to findout that the permeation of fuel from plastic fuel containers isparticularly large at pinch-off parts formed when the container ismolded, as will be explained below.

As mentioned above, multilayered parisons obtained by melt extrusion ofseveral kinds of resins have a cutting face (that is, a cutting facewhere the parison is pinched off with the molds or a surface where it iscut off with a cutter) at the pinch-off part. Because this cutting faceis not covered with the resin with high barrier properties, gas maypermeate through this cutting face.

However, the permeation of gas through the pinch-off parts ofblow-molded containers has hitherto not been realized as a problem. Thisis because the amount of permeation of gas (for example, the amount ofpermeation of oxygen) in polyolefins is in the order of several thousandtimes larger than the amount of permeation of gas in EVOH, andfurthermore the area of the pinch-off part is small compared with thesurface area of the entire container.

However, as the result of the research by the inventors, it became clearfor the first time that the difference between the gasoline permeationamounts of polyolefins and EVOH is in the order of several milliontimes, and that therefore the permeation of fuel through the pinch-offparts of blow-molded containers, which has not been realized as aproblem with the permeation of oxygen, is too large to be ignored.

An example of the related art, which puts its attention on thepermeation of gas through the pinch-off part is disclosed in JapaneseLaid-Open Patent Publication No. 50-100165. However, this publicationexamines only the permeation of oxygen, and fails to disclose or suggestthat the difference between the gasoline permeation amounts ofpolyolefins and EVOH is extremely large. Consequently, it is impossibleto obtain from this document the suggestion that the permeation of fuelthrough the pinch-off part of a blow-molded container is too large to beignored.

To improve the barrier properties of the pinch-off part, thispublication discloses a plastic multilayered container characterized inthat the barrier layer of the multilayered structure is substantiallycontinued at the pinch-off part. However, with such a multilayeredcontainer, it is not possible to attain sufficient contact strength atthe pinch-off part, so that the impact resistance becomes unsatisfactory(see Comparative Example 3 and FIG. 2 of this specification).

In addition to the permeation of fuel through the pinch-off parts asexplained above, another problem of fuel tanks for vehicles is thepermeation of fuel through attached components for fuel containers and,as described above, the portions where the components are attached.

Usually, a vehicle fuel tank is connected by pipe ducts with a filleropening, an engine and a canister. Therefore, the body of the tank isprovided with openings for connecting the tank with these pipe ducts,and the components (such as the connectors for the fuel tank) areinstalled to couple the tank with the pipe ducts. Conventionally, thesecomponents for fuel containers are almost invariably made of apolyolefin (e.g. high-density polyethylene) with poor gasoline barrierproperties. The inventors of the present invention have performedresearch with the object of reducing the permeation of fuel through thecomponents for fuel containers, and have developed a component that ismade of a resin composition including EVOH (Japanese Patent ApplicationNos.11-172151 and 11-172152). Using this resin composition includingEVOH, a sweeping reduction of the amount of fuel permeated through thecomponents for fuel containers was achieved.

However, even changing the conventional components for fuel containersmade of high-density polyethylene into components made of theabove-mentioned EVOH containing resin composition, the barrierproperties that are expected from the barrier properties possessed bythis composition itself were not obtained.

The inventors were the first to find out that the fuel in the containervaporizes from the portions where the components are attached. Forexample, FIG. 5 shows a fuel container made of a multilayered structureincluding a barrier layer 1 and thermoplastic resin layers 2 and 3, inwhich a component 6 is attached to an opening portion of its body. Atthis opening portion, fuel may evaporate and pass through the layersthat are located on the outside with respect to the barrier layer 1(that is, generally speaking, the outer layer 3 made of a thermoplasticresin (B) and an adhesive layer 10) easily.

Thus, the inventors were the first to realize that the permeation offuel through the pinch-off parts and the portions where components areattached is a serious problem, which nobody has considered before. Basedon this insight and further research, the present invention wasaccomplished.

The following is a detailed explanation of the present invention.

The first fuel container in accordance with the present invention is acoextrusion blow-molded fuel container having a container body made of alayered structure, the layered structure comprising: a barrier layermade of a barrier resin (A); and an inner layer and an outer layer madeof a thermoplastic resin (B) that is different from the barrier resin(A); wherein a ratio (X/Y) of a distance (X) between end portions of thebarrier layer at a pinch-off part of the fuel container and an averagethickness (Y) of the container body and a ratio (Y1/Y) between a totalthickness (Y1) of the layers of the container body that are located onthe inside with respect to the barrier layer and an average thickness(Y) of the container body are within predetermined ranges.

The second fuel container in accordance with the present invention is acoextrusion blow-molded fuel container made of a layered structure, thelayered structure at least comprising: a barrier layer made of a barrierresin (A); and an inner layer made of a thermoplastic resin (B) that isdifferent from the barrier resin (A); wherein a cutting face of apinch-off part of the container is covered by a barrier member made of abarrier material (C).

The third fuel container in accordance with the present invention ismade of a layered structure, and the layered structure at leastcomprises: a barrier layer made of a barrier resin (A); and an outerlayer made of a thermoplastic resin (B) that is different from thebarrier resin (A); wherein the fuel container is provided with anopening through its body, wherein a cutting face of a layer at theopening is covered by a barrier member made of a barrier material (C),and wherein the layer covered by the barrier member is located on theoutside with respect to the barrier layer.

The fourth fuel container in accordance with the present invention ismade of a layered structure, and the layered structure at leastcomprises: a barrier layer made of a barrier resin (A); and an outerlayer made of a thermoplastic resin (B) that is different from thebarrier resin (A); wherein the fuel container is provided with anopening, a cut-out or a groove is provided at an outer surface of thefuel container around the opening, and the cut-out or the groove iscovered or filled with a barrier member made of a barrier material (C).

The following is an explanation of the materials that can be used forthe above-noted first to fourth fuel containers.

The barrier resins (A) that can be used for a fuel container of thepresent invention have good barrier properties (liquid and gas barrierproperties) with respect to the fuel filled into the fuel container ofthe present invention. It is preferable that the barrier resin (A) is athermoplastic resin, because it is molded together with thethermoplastic resin forming the inner and/or outer layer. It ispreferable that the gasoline permeation of the barrier resin (A) is atmost 100 g·20 μm/m²·day (measured at 40° C. and 65% RH). Morepreferably, the gasoline permeation of the barrier resin (A) is at most10 g·20 μm/m²·day, even more preferably it is at most 1 g·20 μm/m²·day,yet even more preferably it is at most 0.5 g·20 μm/m²·day, mostpreferably it is at most 0.1 g·20 μm/m²·day. The gasoline that was usedto measure the gasoline permeation is a model gasoline called “Ref. fuelC” of toluene and i-octane mixed at a volume ratio of 1:1.

It should be noted that the fuel container of the present inventiondisplays an advantageous effect also when the fuel filled into thecontainer is a gasoline containing an alcohol such as methanol, ormethyl t-butyl ether (MTBE), that is, so-called oxygen-containinggasoline.

There is no particular limitation concerning the barrier resin, andexamples of possible barrier resins include polyvinyl alcohol resins(A1), polyamides (A2), and aliphatic polyketones (A3).

Of these barrier resins (A), polyvinyl alcohol resins (A1) can beobtained by saponifying a homopolymer of a vinyl ester or a copolymer ofa vinyl ester and another monomer using, for example, an alkalicatalyst.

Vinyl acetate is a typical example of a vinyl ester, but it is alsopossible to use other fatty acid vinyl esters such as vinyl propionateand vinyl pivalate.

The degree of saponification of the vinyl ester component in thepolyvinyl alcohol resin is preferably at least 90%, more preferably atleast 95%, even more preferably at least 97%, and most preferably atleast 99%. When the degree of saponification is less than 90 mol %,there is a possibility that the gas barrier property decreases underhigh humidities. Moreover, for ethylene-vinyl alcohol copolymers (EVOH),the heat stability worsens, and gelled aggregates or fish eyes form moreeasily on the obtained molded article.

If the polyvinyl alcohol resin is made of a blend of at least twopolyvinyl alcohol resins with differing degrees of saponification, thenthe average value calculated by the weight ratio of the compound istaken as the degree of saponification of the blend. The degree ofsaponification of such a polyvinyl alcohol resin can be determined bynuclear electromagnetic resonance (NMR) analysis.

As the polyvinyl alcohol resin (A1) used for the present invention, EVOHis preferable, because it can be used for melt extrusion, has good gasbarrier properties under high humidities, and has excellent gasolinebarrier properties.

The amount of ethylene contained in the EVOH is preferably 5 to 60 mol%. If the amount of ethylene contained in the EVOH is less than 5 mol %,then the gas barrier properties under high humidities decrease, and themelt moldability may worsen as well. Preferably, the amount of ethylenecontained in the EVOH is at least 10 mol %, more preferably at least 15mol %, and most preferably at least 20 mol %. If the amount of ethylenecontained in the EVOH exceeds 60 mol %, then it is difficult to obtainsufficient gas barrier properties. Preferably, the amount of ethylenecontained in the EVOH is at most 55 mol %, more preferably at most 50mol %. Preferably, the degree of saponification of the vinyl estercomponent is at least 85%, more preferably at least 90%, and even morepreferably at least 99%. If the degree of saponification of the vinylester component is less than 85%, then there is a possibility that thegasoline barrier properties and the heat stability worsen. The amount ofethylene contained in the EVOH and its degree of saponification can bedetermined by nuclear electromagnetic resonance (NMR) analysis.

When the EVOH is a blend of at least two kinds of EVOH having differentethylene contents or degrees of saponification, the average ethylenecontent or the average degree of saponification is calculated based onthe blend weight ratio. This average value is designated as the ethylenecontent or the degree of saponification of the blend.

In the case of a blend of two kinds of EVOH, it is preferable that thedifference in the ethylene contents between the two kinds of EVOH is 15mol % or less and that the difference in the degree of saponification is10% or less. If these conditions fail to be satisfied, there is apossibility that the gasoline barrier properties are harmed. From theviewpoint of obtaining good gasoline barrier properties, the differencebetween the ethylene contents is more preferably at most 10 mol % andeven more preferably at most 5 mol %. Similarly, from the viewpoint ofobtaining good gasoline barrier properties, the difference between thedegrees of saponification of the two EVOHs is more preferably at most 7%and even more preferably at most 5%.

A small amount of another monomer may be contained in the polyvinylalcohol resin (A1), especially in EVOH, as a copolymerization component(i.e., as a copolymer unit) within the range not interfering with thepurposes of the present invention. Examples of the monomer that may be acopolymerization component include: α-olefins such as propylene,1-butene, isobutene, 4-methyl-1-pentene, 1-hexene, and 1-octene;unsaturated carboxylic acids such as itaconic acid, methacrylic acid,acrylic acid, and maleic anhydride, and salts, partial or completeesters, nitrites, amides, and anhydrides thereof; vinylsilane compoundssuch as vinyltrimethoxysilane; unsaturated sulfonic acids and theirsalts; alkylthiols; and vinylpyrrolidones.

Among the above, when a vinylsilane compound is contained in EVOH as acopolymerization component in an amount of 0.0002 to 0.2 mol %, theconsistency in melt viscosity of the EVOH with that of the base resinduring coextrusion molding or coinjection molding is improved, allowingfor production of a uniformly molded article. Examples of thevinylsilane compound include vinyltrimethoxysilane,vinyltriethoxysilane, vinyltri(β-methoxy-ethoxy)silane,γ-methacryloyloxypropyltrimethoxysilane. Among these,vinyltrimethoxysilane and vinyltriethoxysilane are preferable.

EVOH containing a boron compound is also effective in improving theconsistency in melt viscosity of EVOH with that of the base resin duringcoextrusion molding or coinjection molding, allowing for production of auniformly molded article even in a process of a long term coextrusion orcoinjection molding. Examples of the boron compound include boric acids,boric acid esters, borates, and boron hydrides. Specifically, the boricacids include boric acid, orthoboric acid, metaboric acid, andtetraboric acid. The boric acid esters include triethyl borate andtrimethyl borate. The borates include alkali metal salts, alkaline-earthmetal salts of the boric acids, borax, and the like. Among thesecompounds, boric acid is preferable.

The content of the boron compound, if contained, is preferably in therange of 20 to 2000 ppm, and more preferably 50 to 1000 ppm, in terms ofthe boron element. With the addition of boron within this range, torquevariation in EVOH during melting by heating is suppressed. If the boroncontent is less than 20 ppm, this effect is minimal. If it exceeds 2000ppm, gelation tends to occur resulting in poor moldability.

It is also effective in improving the layer adhesions and compatibilityto add an alkali metal salt to the EVOH in an amount of 5 to 5000 ppm interms of the alkali metal element.

The added amount of the alkali metal salt is more preferably in therange of 20 to 1000 ppm, and more preferably 30 to 750 ppm, in terms ofthe alkali metal element. The alkali metal in the alkali metal saltincludes lithium, sodium, potassium, and the like. Examples of thealkali metal salt include aliphatic carboxylates, aromatic carboxylates,phosphates, and metal complexes of monovalent metals. Specifically, theyinclude sodium acetate, potassium acetate, sodium phosphate, lithiumphosphate, sodium stearate, potassium stearate, sodium salt ofethylenediaminetetraacetic acid, and the like. Among these, sodiumacetate, potassium acetate, and sodium phosphate are most preferable.

It is also preferable to add a phosphorus compound to the EVOH in anamount of 10 to 500 ppm in terms of the phosphorous element. Adding asuitable amount of a phosphorous compound, it is possible to suppresscoloring as well as the generation of gelled aggregates and fish eyes.These improvements due to the addition of a phosphorous compound areparticularly striking when a molding operation using resin compositionpellets containing EVOH continues for prolonged periods of time and whenrecovering and recycling of the molded article. The kind of phosphoruscompound is not specifically defined, but various kinds ofphosphorus-containing acids such as phosphoric acid and phosphorous acidand salts thereof may be used. Phosphates may be in the form of primaryphosphates, secondary phosphates, or tertiary phosphates, and thecationic species of the phosphates is not specifically defined. Thephosphates are preferably alkali metal salts and alkaline-earth metalsalts. Among these, it is preferable to add the phosphorus compound inthe form of sodium dihydrogenphosphate, potassium dihydrogenphosphate,disodium hydrogenphosphate, or dipotassium hydrogenphosphate.

Preferably, the included amount of the phosphorous compound is at least50 ppm, more preferably at least 70 ppm in terms of the phosphorouselement. Preferably, the included amount of the phosphorous compound isat most 300 ppm, more preferably at most 200 ppm in terms of thephosphate radical. Including a phosphorous compound in this range, thecoloring of the EVOH can be decreased even more, and the gelation willnot occur so easily. If the amount of the phosphorous compound is lessthan 10 ppm, there is a possibility that the coloring during the meltforming process becomes too intense. This tendency becomes especiallyconspicuous when the thermal history is long, so that recovering andrecycling of the molded article becomes difficult. If the amount of thephosphorous compound exceeds 500 ppm, there is a possibility that gelledaggregates and fish eyes tend to occur on the molded article.

It is also possible to add to the EVOH beforehand a thermal stabilizer,an ultraviolet absorber, an antioxidant, a coloring agent, a filler, andother resins (e.g., polyamides and polyolefins) as required. EVOHscontaining a boron compound, an alkali metal salt, a phosphoruscompound, and the like are commercially available.

The melt flow rate (MFR) of the EVOH used in the present invention (190°C., 2160 g load; according to JIS K7210) is preferably in the range of0.1 to 100 g/10 min, more preferably 0.05 to 50 g/10 min, and even morepreferably 0.1 to 10 g/10 min.

The polyamide resin (A2), which is a barrier resin (A), is a polymerhaving an amide bond, and there is no particular limitation concerningit. Examples of suitable polyamide resins (A2) include aliphaticpolyamide homopolymers such as polycaproamide (Nylon-6),polyundecanamide (Nylon- 11), polylaurolactam (Nylon- 12),polyhexamethylene adipamide (Nylon-6,6), and polyhexamethylenesebacamide (Nylon-6,12); aliphatic polyamide copolymers such ascaprolactam/laurolactam copolymer (Nylon-6/12), caprolactamaminoundecanoic acid copolymer (Nylon-6/11), caprolactam/ω-aminononanoicacid copolymer (Nylon-6/9), caprolactam/hexamethylene adipamidecopolymer (Nylon-6/6,6), and caprolactam/hexamethyleneadipamide/hexamethylene sebacamide copolymer (Nylon-6/6,6/6,12); andaromatic polyamides such as a copolymer of adipic acid and metaxylylenediamine and a copolymer of hexamethylenediamine and m- or p-phthalicacid. These polyamides can be used alone or in mixtures of two or more.

Of these polyamides, Nylon-6 is preferable, because of its barrierproperties.

The aliphatic polyketone used for the present invention is a carbonmonoxide-ethylene copolymer. Suitable carbon monoxide-ethylenecopolymers include a copolymer obtained by copolymerizing carbonmonoxide and ethylene and a copolymer obtained by copolymerizing carbonmonoxide and ethylene as the main components and further containing anunsaturated compound other than ethylene as a copolymer component.Suitable unsaturated compounds other than ethylene include α-olefinswith a carbon number of 3 or higher, styrene, diene compounds, vinylesters, and aliphatic unsaturated carboxylic acids (including theirsalts and esters). Suitable copolymers include random copolymers andalternating copolymers, and alternating copolymers are preferable. Withalternating copolymers, higher barrier properties can be obtained,because their crystallinity is high.

With regard to melt stability, it is preferable that the alternatingcopolymer contains an unsaturated compound other than carbon monoxideand ethylene as a copolymer component, because the melting point of sucha copolymer is high, and thus, the melt-stability of the copolymerincreases. As an unsaturated compound that is suitable as the copolymercomponent, α-olefins are preferable, and examples of suitable α-olefinsinclude propylene, butene-1, isobutene, pentene- 1,4-methylpentene- 1,hexene- 1, octene- 1, and dodecene- 1. Among these, α-olefins with acarbon number of 3 to 8 are preferable, and propylene is particularlypreferable. It is preferable that the amount of α-olefin is 0.5 to 7 wt% of the resulting polyketone, because this ensures an appropriatecrystallinity and melt stability.

For the diene compound of the copolymer component in the polyketone, adiene with a carbon number of 4 to 12 is preferable, and suitableexamples include butadiene, isoprene, 1,5-hexadiene, 1,7-octadiene, and1,9-dekadiene. Suitable vinyl esters for the copolymer component in thepolyketone include vinyl acetate, vinyl propionate, and vinyl pivalate.Suitable aliphatic unsaturated carboxylic acids include acrylic acid,methacrylic acid, maleic anhydride, maleic acid, and itaconic acid.Suitable aliphatic unsaturated carboxylic esters include acrylic esters,methacrylic esters, maleic monoesters, maleic diesters, fumaricmonoesters, fumaric diesters, itaconic monoesters, and itaconicdiesters. The esters include methyl esters, ethyl esters and other alkylesters. Suitable salts of aliphatic unsaturated carboxylic acids includesalts of acrylic acid, salts of maleic acid, and salts of itaconic acid,and these salts can be univalent or divalent metal salts. For themonomers for the copolymer components, it is possible to use not onlyone kind but also to combine two kinds or more.

A conventional method can be used for the manufacture of the polyketone.For example, one of the methods disclosed in U.S. Pat. No. 2,495,286,and Japanese Laid-Open Patent Publication Nos. 53-128690, 59-197427,61-91226, 62-232434, 62-53332, 63-3025, 63-105031, 63-154737, 1-149829,1-201333, and 2-67319 can be employed, but there is no particularlimitation concerning these methods.

Preferably, the melt flow rate (MFR) of the polyketone used in thepresent invention is 0.01 to 50 g/10 min (at 230° C. and a load of 2160g), most preferably 0.1 to 10 g/10 min. When the MFR is in these ranges,the flowability of the resin is excellent, and the moldability too isexcellent.

With regard to the gasoline barrier properties, polyvinylalcohol resinsand polyamides are preferable for the barrier resin (A) used for thepresent invention, and EVOH, which is a polyvinylalcohol resin, isespecially preferable.

Suitable thermoplastic resins (B) used for the inner layer, outer layeror intermediate layers in a fuel container according to the presentinvention include olefin homopolymers and copolymers (e.g.,linearlow-density polyethylene, low-density polyethylene, medium-densitypolyethylene, high-density polyethylene, ethylene-vinyl acetatecopolymer, ethylene-propylene copolymer, polypropylene,propylene-α-olefin copolymer (with an α-olefin with a carbon number of 4to 20), polybutene, polypentene, and the like), polystyrene, polyvinylchloride, polyvinylidene chloride, acrylic resin, vinyl ester resin,polyurethane elastomer, polycarbonate, chlorinated polyethylene,chlorinated polypropylene. Of these, it is preferable to usepolypropylene, polyethylene, ethylene-propylene copolymer,ethylene-vinyl acetate copolymer, or polystyrene.

If the container of the present invention is a coextrusion blow-moldedcontainer, it is preferable to use high-density polyetylene,particularly polyethylene with a density of at least 0.93 g/cm³, for thethermoplastic resin (B). For such a high-density polyethylene, it ispossible to select an appropriate product among those commerciallyavailable. With regard to the rigidity, impact resistance, moldability,drawdown resistance, and gasoline resistance, it is preferable that thedensity of the high-polyethylene is 0.95 to 0.98 g/cm³, more preferably0.96 to 0.98 g/cm³. Moreover, the melt flow rate (MFR) of thehigh-density polyethylene is preferably 0.01 to 0.5 g/10 min (at 190° C.and a load of 2160 g), more preferably 0.01 to 0.1 g/10 min (at 190° C.and a load of 2160 g).

In the fuel container of the present invention, it is preferable toadhere the barrier layer made of the barrier resin (A) and the innerlayer and/or the outer layer made of the thermoplastic resin (B)together with an adhesive layer made of an adhesive resin (D). For suchan adhesive resin, a carboxylic acid modified polyolefin is appropriate.The carboxylic acid modified polyolefin is a copolymer of an olefin,particularly an α-olefin, and an unsaturated carboxylic acid or itsanhydride. This includes polyolefins having carboxyl groups in themolecule and polyolefins having carboxyl groups in the molecule whereinall or some of the carboxyl groups are present in the form of metalsalts. For the carboxylic acid modified polyolefin, a modifiedpolyolefin including a carboxyl group is preferable, which can beobtained by the chemical bonding (for example, obtained by an additionreaction or a graft polymerization) of an unsaturated carboxylic acid orits anhydride to a polyolefin.

Suitable polyolefins serving as the base polymer for the carboxylic acidmodified polyolefin include homopolymers such as polyethylene (forexample, high-density polyethylene (HDPE), low-density polyethylene(LDPE), linear low-density polyethylene (LLDPE), very low-densitypolyethylene (VLDPE) and the like), polypropylene, and polybutene; andcopolymers (for example, ethylene-vinyl acetate copolymer andethylene-(meth)acrylate copolymer) of an olefin and a comonomer (such asa vinyl ester, or unsaturated carboxylic ester) that can copolymerizewith the olefin. Of these, linear low-density polyethylene,ethylene-vinyl acetate copolymer (including 5 to 55% vinyl acetate) andethylene-ethyl acrylate copolymer (including 8 to 35% ethyl acrylate)are preferable, and linear low-density polyethylene and ethvlene-vinylacetate copolymer are particularly preferable.

Examples of the aforementioned unsaturated carboxylic acid and itsanhydride that can be used for the preparation of the carboxylic acidmodified polyolefin include acrylic acid, methacrylic acid, maleic acid,fumaric acid, itaconic acid, monomethyl maleate, monoethyl maleate, andmonomethyl fumarate, and of these, in particular acrylic acid andmethacrylic acid are preferable. The included amount of unsaturatedcarboxylic acid is preferably 0.5 to 20 mol %, more preferably 2 to 15mol %, even more preferably 3 to 12 mol %. Examples of the unsaturatedcarboxylic anhydride include itaconic anhydride and maleic anhydride,and in particular maleic anhydride is preferable. The included amount ofunsaturated carboxylic anhydride is preferably 0.0001 to 5 mol %, morepreferably 0.0005 to 3 mol %, even more preferably 0.001 to 1 mol %.

Examples of other monomers that can also be included as copolymercomponents in the carboxylic acid modified polyolefin are vinyl esterssuch as vinyl acetate and vinyl propionate; unsaturated carboxylicesters such as methyl acrylate, ethyl acrylate, isopropyl acrylate,isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methylmethacrylate, isobutyl methacrylate, and diethyl maleate; and carbonmonoxide.

Examples of metals for the metal salt of the carboxylic acid modifiedpolyolefin are alkali metals such as lithium, sodium, and potassium;alkaline earth metals such as magnesium and calcium; and transitionmetals such as zinc. The neutralization degree in the metal salt of thecarboxylic acid modified polyolefin is preferably less than 100%, morepreferably at most 90%, and even more preferably at most 70%.Furthermore, the neutralization degree is preferably at least 5%, morepreferably at least 10%, and even more preferably at least 30%.

The melt flow rate (MFR) (at 190° C. and a load of 2160 g) of thecarboxylic acid modified polyolefin used for the present invention ispreferably 0.01 to 50 g/10 min, more preferably 0.05 to 30 g/10 min, andeven more preferably 0.1 to 10 g/10 min. These carboxylic acid modifiedpolyolefins can be used alone or as mixtures of two or more.

Like the barrier resin (A), the barrier materials (C) that can be usedfor the present invention have good barrier properties (liquid and gasbarrier properties) with respect to the fuel filled into the fuelcontainer. Preferably, the gasoline permeation (measured at 40° C. and65% RH) of the barrier material (C) used for the present invention is atmost 0.1 times the gasoline permeation (measured at 40° C. and 65% RH)of the thermoplastic resin (B). More preferably, the gasoline permeationof the barrier material (C) is at most 0.05, more preferably at most0.01 times the gasoline permeation of the thermoplastic resin (B).

If the gasoline permeation amount of the barrier material (C) exceeds0.1 times the gasoline permeation amount of the thermoplastic resin (B),then there is a possibility that its capability as a barrier materialbecomes insufficient, and that the amount of fuel permeating through thepinch-off parts and the openings of the tank body cannot be decreasedsufficiently.

Preferably, the gasoline permeation amount of the barrier material (C)used for the present invention is at most 400 g·20 μ/m² day (measured at40° C. and 65% RH). If the gasoline permeation amount exceeds 400 g·20μm²·day (measured at 40° C. and 65% RH), then there is a possibilitythat its capability as a barrier material becomes insufficient, and thatthe amount of fuel permeation through the pinch-off parts and theopenings of the tank body cannot be decreased sufficiently. Morepreferably, the gasoline permeation amount of the barrier material (C)is at most 100 g·20 μm²·day, even more preferably at most 50 g·20μ/m²·day, particularly preferably at most 10 g·20 μ/m²·day, and mostpreferably at most 1 g·20 μg/m²·day (all measured at 40° C. and 65% RH).

For the barrier material (C), it is suitable to use at least oneselected from the group consisting of metal foil, epoxy resin,polyvinylidene chloride resin, polyvinylalcohol resin, polyamide resin,polyester resin, and fluorocarbon resin. Of these, it is preferable touse metal foil because of its easy handling. In particular, it ispreferable to employ a laminate obtained by the application of anadhesive material that is adhesive with respect to the body of thecontainer onto the metal foil, like an aluminum adhesive tape. There areno particular limitation concerning the metal foil, and it is possibleto use a metal vapor deposition film or a vapor deposition film of ametal oxide, but with regard to availability and handling, an aluminumfoil is preferable.

If the barrier material (C) is a thermoplastic resin, then the sameresin as for the barrier resin (A) can be used for the barrier material(C). As long it does not obstruct the object of the present invention,it is also possible to blend this barrier material (C) with suitableamounts of other thermoplastic resins to improve its mechanical strengthand moldability. Suitable other thermoplastic resins include any kindsof polyolefins (such as polyethylene, polypropylene, poly-1-butene,poly-4-methyl-1-pentene, ethylene-propylene copolymer, copolymer ofethylene and α-olefin with a carbon number of at least four, copolymerof polyolefin and maleic anhydride, ethylene-vinyl ester copolymer,ethylene-acrylate copolymer as well as modified polyolefins obtained bygraft modification of these polymers with unsaturated carboxylic acidsor derivatives thereof, polystyrene, polyacrylonitryl, and the like.

The following is an explanation of a first to fourth fuel container inaccordance with the present invention.

The first fuel container of the present invention is a coextrusionblow-molded container. The ratio (X/Y) of the distance (X) between endportions of the barrier layer at the pinch-off part of the container andthe average thickness (Y) of the container body is at least {fraction(1/10000)} and at most {fraction (1/10)}. The ratio (Y1/Y) of the totalthickness (Y1) of the layers of the container body that are located onthe inside with respect to the barrier layer and the average thickness(Y) of the container body is at least {fraction (3/10)} and at most{fraction (7/10)}. Because of this configuration, the container hasfavorable barrier properties, and has the advantages of an excellentdart-impact strength and has little deformation (details will beexplained below).

The aforementioned “distance (X) between end portions of the barrierlayer at a pinch-off part of the container” refers to the distancebetween the opposing end portions of the barrier layer where the barrierlayers are closest to one another in a cross-section taken in thethickness direction of the container through the the pinch-off part, asshown in FIG. 1. “Average thickness (Y) of the container body” means theaverage thickness of the body of the fuel container of the presentinvention. “Total thickness (Y1) of the layers of the container bodythat are located on the inside with respect to the barrier layer” in thecontainer body refers to the thickness of the layers that are located onthe inside with respect to the barrier layer in a cross-section taken inthe thickness direction of the container through the container body asshown in FIG. 1.

As mentioned above, in the first fuel container of the presentinvention, the lower limit for the ratio (X/Y) of the distance (X)between the end portions of the barrier layer and the average thickness(Y) of the container body is {fraction (1/10000)}, and it is preferably{fraction (1/5000)}, more preferably {fraction (1/1000)}. When the ratio(X/Y) is less than {fraction (1/10000)}, the strength of the pinch-offpart becomes insufficient, and the impact resistance of a coextrusionblow-molded container with such a pinch-off part becomes insufficient.

The upper limit for the ratio (X/Y) of the distance (X) between the endportions of the barrier layer and the average thickness (Y) of thecontainer body is {fraction (1/10)}, preferably {fraction (1/20)}, morepreferably {fraction (1/40)}, and even more preferably {fraction(1/100)}. When this ratio (X/Y) exceeds {fraction (1/10)}, the amount ofthe content permeating through the pinch-off part cannot be suppressedsufficiently. If this ratio (X/Y) exceeds {fraction (1/10)}, deformationtends to occur more easily in the coextrusion blow-molded containerafter the molding (see Comparative Examples 1 and 2 of thisspecification).

There is no particular limitation concerning the method to ensure thatthe pinch-off part has the above-mentioned favorable ratio (X/Y), but itis preferable to use suitable molds and carry out the molding with asuitable mold cramping force.

FIG. 4 shows several schematic views of examples of molds having apinch-off part forming section and the pinch-off parts obtained withthese molds. The mold design for obtaining pinch-off in theabove-mentioned preferable ranges of the ratio (X/Y) is discretionary,but FIGS. 4a and 4 d show preferable examples of molds having apinch-off part forming section.

To control the ratio (X/Y), it is also preferable that the MFR of theresin of the barrier layer (MFRbarrier) and the MFR of the resin of theinnermost layer (MFRinside) satisfy the following relation:

8≦MFRbarrier/MFRinside≦100  (1)

Here, MFRbarrier and MFRinside both refer to values measured at 190° C.and a load of 2160 g. However, if the melting point is about 190° C. orhigher, then the measurement is carried out at a load of 2160 g at aplurality of temperatures at or above the melting point, the inverses ofthe absolute temperatures are marked on the horizontal axis and thelogarithm of the MFR is plotted on the vertical axis in asemi-logarithmic graph, and the MFR is determined by extrapolation to190° C.

Preferably, MFRbarrier/MFRinside is at least 10, more preferably atleast 15. If MFRbarrier/MFRinside is less than 8, there is a possibilitythat the ratio (X/Y) becomes less than {fraction (1/1000)} due toflowing of the resin for the innermost layer during the molding.

Preferably, MFRbarrier/MFRinside is at most 80, more preferably at most70. If MFRbarrier/MFRinside exceeds 100, there is a possibility that theconsistency of the viscosities of the resin of the barrier layer and theresin of the innermost layer becomes poor, and that the moldability ofthe coextrusion blow-molded container becomes unsatisfactory.

As mentioned above, in the first fuel container of the presentinvention, the ratio (Y1/Y) of the total thickness (Y1) of the layers ofthe container body that are located on the inside with respect to thebarrier layer and the average thickness (Y) of the container body is atleast {fraction (3/10)} and at most {fraction (7/10)}. Preferably, thisratio (Y1/Y) is at least {fraction (32/100)}, and more preferably atleast {fraction (35/100)}. Also, preferably this ratio (Y1/Y) is at most{fraction (65/100)}, and more preferably at most {fraction (60/100)}. Ifthe ratio (Y1/Y) is below {fraction (3/10)}, the impact resistance atthe pinch-off part becomes unsatisfactory, and if the ratio (Y1/Y)exceeds {fraction (7/10)}, the barrier properties become unsatisfactory.By keeping the ratio (Y1/Y) in these ranges, sufficient barrierproperties as well as sufficient impact resistance can be attained.

Among the related art, a technology is disclosed (Japanese Laid-OpenPatent Publication No.9-29904) in which the barrier layer is arrangedcloser to the inner layer to improve the gas barrier properties of thefuel tank. Example 6 of this publication describes a coextrusionblow-molded bottle with a thickness ratio (I/O)={fraction (4/96)},wherein “I” denotes the total thickness of all layers that are locatedon the inside with respect to the barrier layer and “O” denotes thetotal thickness of all layers that are located on the outside withrespect to the barrier layer. With such a bottle, the ratio (X/Y) of thedistance (X) between end portions of the barrier layer at the pinch-offpart and the average thickness (Y) of the container body is almostalways at least {fraction (1/10000)} and at most {fraction (1/10)},obtaining high barrier properties, even without taking any exceptionalmeasures with regard to the molds or the molding conditions when cuttingoff the parison. However, in this coextrusion blow-molded bottle, thetotal thickness of the layers on the inside with respect to the barrierlayer is insufficient at the pinch-off part (see FIG. 3). The strengthof the pinch-off part is maintained mainly by fusion of the layerslocated on the inside with respect to the barrier layer at the pinch-offpart. Consequently, in this configuration, the thickness of the layerlocated inside the barrier layer at this portion is extraordinary thin,and thus the impact resistance at the pinch-off part becomesunsatisfactory (see Comparative Example 4 of this specification).

In the first fuel container of the present invention, the ratio (H/L) ofthe length (L) of the pinch-off part and the height (H) of the pinch-offpart shown in FIG. 1 is preferably set to 0.1 to 3. The lower limit ofthis ratio (H/L) is preferably 0.2, and more preferably 0.3. The upperlimit of this ratio (H/L) is preferably 2.5, and more preferably 2.Keeping the ratio (H/L) within these ranges is preferable, because thisachieves both good barrier properties and impact resistance. If theratio (H/L) is less than 0.1, there is a possibility that thesuppression of fuel in the container permeating through the pinch-offpart becomes insufficient, and if the ratio (H/L) is higher than 3, thenthere is a possibility that the impact resistance of the pinch-off partis not high enough.

There is no particular limitation concerning the method with which theratio (H/L) is kept in these preferable ranges. If the coextrusionblow-molded container is small, the parison is often pinched off withthe molds, so that it is preferable to arrange the molds appropriately.If the coextrusion blow-molded container is large, such as a fuel tankfor a vehicle, the parison is mostly held and press-sealed with themolds, but not cut off with the molds, and the portion that sticks outfrom the container surface is often cut off with a cutter at the desiredheight. Therefore, to keep the ratio (H/L) in a preferable range, it ispreferable to adjust the cutter or the like to an appropriate cuttingposition.

Thus, although it used to be difficult to achieve both good barrierproperties and impact resistance at the pinch-off part, a fuel containerwith excellent barrier properties and impact resistance can be obtainedby employing this configuration of a first fuel container of the presentinvention.

The mold temperature when the first fuel container of the presentinvention is produced by coextrusion blow-molding is preferably 5 to 30°C., more preferably 10 to 30° C., and even more preferably 10 to 20° C.If the mold temperature is less than 5° C., dew forms easily on the moldsurface, and there is a possibility that the outward appearance of themolded article is poor. On the other hand, if the mold temperatureexceeds 30° C., there is a possibility that the productivity decreasesdue to the long cooling times of the resin, and if the resin cannot becooled sufficiently, there is a possibility that deformation occursafter the coextrusion blow-molding.

As mentioned above, the first fuel container of the present invention isa coextrusion blow-molded fuel container, which is a layered producthaving a barrier layer made of a barrier resin (A) and an outer layerand an inner layer made of a thermoplastic resin (B). There is noparticular limitation concerning the layering structure, and consideringmoldability and cost factors, typical examples of suitable layeringstructures include thermoplastic resin layer/barrier layer/thermoplasticresin layer and thermoplastic resin layer/adhesive resin layer/barrierlayer/adhesive resin layer/thermoplastic resin layer. The thermoplasticresins for the inner and the outer layers can be identical resins ordifferent kinds of resins.

With regard to the rigidity, impact resistance, moldability, drawdownresistance, and gasoline resistance, it is preferable that the layeringstructure used for the fuel container is high-densitypolyethylene/adhesive resin layer/barrier layer/adhesive resinlayer/high-density polyethylene.

When the coextrusion blow-molded container is produced, the formation ofburr is unavoidable. It is possible to remelt this burr together withunacceptable pieces of products and use it for a recovered layer.Forming such recovered layers decreases the loss of resin used for themanufacture of the container and enhances the recycling of the resins.For the recovered layer, it is possible to use a resin or a resinmixture, for example, obtained by remelting a multilayered structuremade of a thermoplastic resin and a barrier layer (and possibly anadhesive resin layer). Generally, the mechanical strength of such arecovered layer is often weaker than that of a layer made of athermoplastic resin of a single kind. If the container is subjected toan impact from the outside, a corresponding stress acts on the side ofthe inner layers of the container, generating deformation of thecontainer, which may in some cases even lead to fractures. Therefore, itis particularly preferable that the recovered layer is arranged on theoutside with respect to the barrier layer. Furthermore, if large amountsof resin have to be recycled, such as when a lot of burr is formed, itis recommendable to arrange recovered layers on both sides of thebarrier layer.

With the first coextrusion blow-molded fuel container of the presentinvention, the barrier properties at the pinch-off part do notdeteriorate, and the dart-impact strength does not become insufficientdue to the failure to achieve a sufficient contact strength.

As mentioned above, the second fuel container of the present inventionis a coextrusion blow-molded fuel container, which is a layered producthaving at least a barrier layer made of a barrier resin (A), and aninner layer made of a thermoplastic resin (B) that is different from thebarrier resin (A). The cutting face of the pinch-off part of thiscontainer is covered by a barrier member made of a barrier material (C).FIG. 6 is a schematic view showing the pinch-off part of the second fuelcontainer. This container is made of a layered product having a barrierlayer 1, an inner layer 2 and an outer layer 3, and a pinch-off part 4is covered by a barrier member 5.

If the pinch-off part of the fuel container of the present invention iscovered with a barrier member, the covering of the pinch-off part can bepartial or complete. With regard to obtaining sufficient gasolinebarrier properties, it is preferable that at least the cutting face ofthe layer (here, this is the inner layer 2) surrounded by the barrierlayer (in FIG. 6, between end portions of barrier layer 1 and 1) iscovered by the barrier member 5, as shown in FIG. 6. Covering thisportion completely effectively suppresses the permeation of fuel throughthe pinch-off part. It is also recommendable to cover the entire cut-offface of the pinch-off part.

As mentioned above, the third fuel container of the present invention isa layered product having at least a barrier layer made of a barrierresin (A), and an outer layer made of a thermoplastic resin (B) that isdifferent from the barrier resin (A). In the opening portion provided inthe body of the container, the cutting face of the layer located on theoutside with respect to the barrier layer is covered with a barriermember.

FIG. 7 is a schematic view showing an example of the opening portion ofsuch a container. This container is made of a layered product having abarrier layer 1, an inner layer 2 and an outer layer 3. In the openingportion provided in the body of the container, at least the cutting faceof the layer located on the outside with respect to the barrier layer 1(here, this is the outer layer 3) is covered with a barrier member 51.Covering completely at least this portion of the entire cutting faceeffectively suppresses the permeation of fuel through the openingprovided in the body of the container. It is also possible to cover theentire cutting face of the opening of the layered product.

As shown in FIGS. 8a and 8 b, the same effect can be attained bymounting a component for fuel containers 61 made of the barrier material(C) on the opening portion provided in the body of the container as abarrier member to cover at least the cutting face of the outer layer 3of the container.

In the second and third fuel containers of the present invention, thereis no particular limitation concerning the method for covering thecutting face of the pinch-off part of the container or the openingportion provided in the body of the fuel container with a barriermember. Suitable methods include applying a barrier material (C) havingadhesiveness with respect to the body of the fuel container to thecutting face of the pinch-off part and solidifying or drying the same,and as a result, covering the pinch-off part with a barrier member;applying to the cutting face an adhesive having adhesiveness withrespect to both the body of the fuel container and the barrier material,and then covering the cutting face with a barrier member; uniting thebarrier material (C) with a substrate having adhesiveness with respectto the fuel container, and then covering the cutting face with theresulting barrier member (such as aluminum adhesive tape for example);bonding a molded article (barrier member) made of the barrier material(C) to the cutting face by thermal fusion or via an adhesive to coverthe cutting face. There is no particular limitation concerning themolded article made of the barrier material (C), but it is preferable touse a film, a sheet, a component for fuel containers, or the like.

Of these covering methods, uniting the barrier material (C) with asubstrate having adhesiveness with respect to the fuel container, andthen covering the cutting face with the resulting barrier member (suchas aluminum adhesive tape for example); and bonding a molded articlemade of the barrier material (C) to the cutting face by thermal fusionor via an adhesive to cover the cutting face are preferable with regardto the facility with which they can be carried out.

As mentioned above, the fourth fuel container of the present inventionis a layered product having at least a barrier layer made of a barrierresin (A), and an outer layer made of a thermoplastic, resin (B) that isdifferent from the barrier resin (A). An opening is provided in the bodyof the container, and a cutout or a groove is provided in the outersurface of the container around this opening. The cutout or groove arecovered or filled with the barrier material (C).

The following is an explanation of such a fourth fuel container that isprovided with a cutout around the opening. As shown in FIG. 9a, aportion of the layered product around the opening provided in the bodyof the container, including the material at the opening, is cut away,forming a cutout 71. The inner surface of this cutout is covered with abarrier material, for example by applying (e.g., adhering) asingle-layer or multilayered sheet made of the barrier material (C) toit. Alternatively, the inner surface is covered with a barrier member bymounting a molded article made of the barrier material (C). For example,a component for fuel containers 62 is mounted by thermal fusion and theinner surface of the cutout is covered, as shown in FIGS. 9 a and 9 b.The molded article made of the barrier material (C) can be, for example,a single-layer sheet-shaped molded product made of the barrier material(C), or a multilayered structure having at least one layer made of thebarrier material (C). Covering the cutting face in this manner, inparticular by mounting an article by thermal fusion is, with respect toworkability, preferable to the method for covering the cutting faceshown in FIG. 8.

The depth of the cutout can be chosen as appropriate, but a depth of 0.1to 0.8 times the average thickness (Y) of the container body ispreferable. More preferably, the depth of the cutout is at least 0.2times, even more preferably at least 0.3 times the average thickness (Y)of the container body. Furthermore preferably, the depth of the cutoutis at most 0.75 times, even more preferably at most 0.7 times theaverage thickness (Y) of the container body. If the depth of the cutoutis less than 0.1 times the average thickness (Y) of the container body,there is a possibility that the effect of improving the barrierproperties becomes unsatisfactory. Moreover, if the depth of the cutoutexceeds 0.8 times the average thickness (Y) of the container body, thereis a possibility that the mechanical strength of the fuel container bodyaround the cutout becomes unsatisfactory.

With regard to the mechanical strength around the opening of thecontainer body, it is preferable that the depth of the cutout is atleast 0.2 and less than 1 times the total thickness (Y2) of the layerslocated on the outside with respect to the barrier layer 1. Morepreferably, the depth of the cutout is at least 0.3, even morepreferably at least 0.5 times the total thickness (Y2). If the depth ofthe cutout is less than 0.2 times the total thickness (Y2), there is apossibility that the effect of improving the gasoline barrier propertiesbecomes insufficient. With regard to obtaining thermal fusibility withthe molded article made of the barrier material (C), the depth of thecutout is more preferably at most 0.999, even more preferably at most0.995, and particularly preferably at most 0.99 times the totalthickness (Y2).

When particularly much weight is given to the gasoline barrierproperties, it is preferable that the depth of the cutout is equal to ormore than the total thickness (Y2). In this configuration, the barriermember blocks the fuel permeation path through the layer located on theoutside with respect to the barrier resin (A) without a gap, so thatextremely good gasoline barrier properties can be obtained. If the depthof the cutout is equal to the total thickness (Y2), then the barrierlayer is exposed, so that when the molded article made of the barriermaterial (C) is thermally fused to cover the cutting face of the cutout,there is a possibility that the thermal fusibility is insufficient. Onthe other hand, if the depth of the cutout exceeds the total thickness(Y2), there is a possibility that the mechanical strength of theperiphery of the cutout becomes insufficient.

In another embodiment of the fourth fuel container of the presentinvention, a groove is provided in the outer surface of the containeraround the opening, and this groove is filled or covered with a barriermember.

This groove is provided at an arbitrary position around the opening, andit is preferable that the groove is arranged so as to enclose theopening completely. With such a configuration, the permeation path canbe blocked completely, which enhances the gasoline barrier properties.If the groove encloses the opening completely, it is preferable that thearea of the portion enclosed by the groove (area including the opening)is 1.1 to 50 times the area of the opening. With regard to theprocessability for making the groove, the area of the portion enclosedby the groove is more preferably at most 30, even more preferably atmost 10, and particularly preferably at most 5 times the area of theopening. Furthermore, it is preferable that the groove enclosing theopening is circular, because this makes it easy to make a groove thatencloses the opening completely.

The inner surface of the groove is covered by a barrier member, or theentire groove is filled with a barrier member. There is no particularlimitation concerning the method for such covering or filling.

Suitable methods for covering the inner surface of the groove with abarrier member include applying to the inner surface of the groove anadhesive having adhesiveness with respect to both the fuel containerbody and the barrier member and then covering the inner surface of thegroove with a barrier member; covering the inner surface of the groovewith a layered product (such as aluminum adhesive tape) made of thebarrier material (C) and an adhesive; applying to the inner surface ofthe groove the barrier material (C) having adhesiveness with respect tothe fuel container and then solidifying or drying it.

Suitable methods for filling the groove with a barrier material includefilling into the groove 72 a barrier material (C) having adhesivenesswith respect to the fuel container body, and solidifying or drying it,as shown in FIGS. 10a and 10 b. In this case, the gasoline barrierproperties, which are the effect of the present invention, can beattained even if the barrier material (C) is bonded by pseudo-adhesionto the outer layer 3 and the barrier layer 1. However, with regard tomechanical strength, it is preferable that the barrier material (C)adheres firmly to the fuel tank body (that is, the outer layer 3 and thebarrier layer 1). If the method employed is filling the barrier material(C) having adhesiveness with respect to the fuel container body into thegroove and solidifying or drying it, then it is particularly preferableto mount a component for fuel containers 63 made of the barrier material(C) to the opening, as shown in FIG. 10c, because this makes it easierto achieve sufficient gasoline barrier properties. The barrier material(C) constituting the component for fuel containers 63 can be the same orcan be different from the barrier material (C) filled into the groove72. The component for fuel containers 63 can be a single-layer moldedproduct made of the barrier material (C), or a multilayered moldedproduct having at least one layer made of the barrier material (C).

As the method for filling the groove with a barrier material (C), amethod in which a molded article made of the barrier material (C), forexample a component for fuel containers, is thermally fused with thegroove is also recommended.

Thus, the fourth fuel container, which is provided with a cutout or agroove whose inner surface is covered or filled, is preferable to thesecond fuel container, in which the cutting face of the opening iscovered directly by the barrier member, because it avoids direct contactbetween the barrier member and the fuel. The barrier member shows goodbarrier properties with respect to the fuel inside the container, sothat deterioration due to direct contact hardly occurs, but when it isat a flow path surface of the fuel, there is a possibility that thebarrier member peels off due to physical forces over long usage periods.

The method of thermally fusing components for fuel containers made ofthe barrier material (C) into the cutout or the groove is preferable tothe method, in which a component for fuel containers made of the barriermaterial (C) is thermally fused with the cutting face of the opening(see FIG. 8). This is because in the former method, thermal fusion canbe carried out more easily.

It is preferable that the depth of the groove is 0.1 to 0.8 times theaverage thickness (Y) of the container body. Preferably, the depth ofthe groove is at least 0.2 times, more preferably at least 0.3 times theaverage thickness (Y) of the container body. Preferably, the depth ofthe groove is at most 0.75 times, more preferably at most 0.7 times theaverage thickness (Y) of the container body. If the depth of the grooveis less than 0.1 times the average thickness (Y) of the container body,there is a possibility that the gasoline barrier properties cannot beimproved sufficiently. Furthermore, if the depth of the groove is morethan 0.8 times the average thickness (Y) of the container body, there isa possibility that the mechanical strength of the fuel container body atthe periphery of the groove becomes insufficient.

With regard to the mechanical strength at the periphery of the opening,it is preferable that the depth of the groove is at least 0.2 and lessthan 1 times the total thickness (Y2) of the layers located on theoutside with respect to the barrier layer, more preferably at least 0.3,even more preferably at least 0.5 times the total thickness (Y2) of thelayers on the outside with respect to the barrier layer. If the depth ofthe groove is less than 0.2 times the total thickness (Y2) of the layerson the outside with respect to the barrier layer, there is a possibilitythat the gasoline barrier properties cannot be improved sufficiently.Considering the thermal fusability with molded articles made of thebarrier material (C), the depth of the groove is preferably at most0.999, more preferably 0.995 times the total thickness (Y2). When givingparticular weight to the thermal fusability, the depth of the groove ispreferably at most 0.99 times the total thickness (Y2).

When giving particular weight to the gasoline barrier properties, it ispreferable that the depth of the groove is equal to or more than thetotal thickness (Y2). With such an embodiment, the permeation path ofthe fuel through the layers located on the outside with respect to thebarrier layer can be blocked without a gap, so that extremely goodgasoline barrier properties can be obtained. If the depth of the cutoutis equal to the total thickness (Y2), then the barrier layer is exposed.Therefore, when the molded article made of the barrier material (C) isthermally fused to cover the cutting face of the groove, there is apossibility that the thermal fusibility is insufficient. On the otherhand, if the depth of the cutout exceeds the total thickness (Y2), thereis a possibility that the mechanical strength of the periphery of theopening becomes insufficient. It should be noted that the barrier layercan also be configured as two or more layers, and in such a case, thetotal thickness of the layers that are outside the outermost barrierlayer is regarded as the total thickness (Y2).

There is no particular limitation concerning the configuration of thelayered article constituting the second to fourth fuel container of thepresent invention, and considering moldability and costs, typicalexamples of suitable configurations include (inside) B/A/B (outside),(inside) B/Tie/A (outside), (inside) B/Tie/A/The/B (outside), (inside)B/Tie/A/Tie/A/Tie/B (outside), wherein “A” denotes barrier layers madeof the barrier resin (A), “B” denotes layers made of the thermoplasticresin (B), and “The” denotes adhesive layers made of the adhesive resin(D). When there are two or more barrier layers, layers made of thethermoplastic resin (B) or adhesive layers, then these layers can bemade of the same resin or of different resins.

When the fuel container of the present invention is used for a fuel tankof motor vehicles, then the layering structure (inside) B/Tie/A/Tie/B(outside) is particularly preferable with regard to rigidity, impactresistance, moldability, drawdown resistance, and gasoline resistance.

There is no particular limitation concerning the thickness of the layersof the fuel container of the present invention, but considering gasolinebarrier properties, mechanical strength, and manufacturing costs of thefuel container, it is preferable that the thickness of the barrier layeris 0.1 to 20% of the total thickness of all layers. The thickness of thebarrier layer is preferably at least 0.5%, and more preferably at least1% of the total thickness of all layers. Furthermore, the thickness ofthe barrier layer is preferably at most 15%, and more preferably at most10% of the total thickness of all layers. If the thickness of thebarrier layer is less than 0.1% of the total thickness of all layers,then there is a possibility that the gasoline barrier properties becomeinsufficient. When the thickness of the barrier layer exceeds 20%, thenthere is a possibility that the mechanical strength is insufficient, andthat the costs are higher. If there is a plurality of barrier layers,then the total thickness of barrier layers is regarded as the thicknessof the barrier layer.

Considering the suppression of the amount of fuel permeating through thecutting face of the opening provided in the body of the container, it ispreferable that the ratio (Y2/Y) of total thickness (Y2) of the layerslocated on the outside with respect to the barrier layer and the averagethickness (Y) of the container body is at most {fraction (45/100)}. Morepreferably, the ratio (Y2/Y) is at most {fraction (40/100)}, even morepreferably {fraction (35/100)}, and particularly preferably at most{fraction (30/100)}. As shown in FIG. 5, the fuel in the containerpermeates to the outside through the layers located on the outside withrespect to the barrier layer, so that by reducing the total thickness(Y2) of the layers located on the outside with respect to the barrierlayer, the amount of fuel permeating from the fuel container can be maderelatively small.

There is no particular lower limit with regard to the ratio (Y2/Y), andthe barrier layer can also be the outermost layer. However, fuelcontainers in which the barrier layer is the outermost layer may be notpreferable with regard to mechanical strength and thermal fusabilitywith components that will be attached to the container. Therefore, inthe fuel container of the present invention, it is preferable that thecontainer has a barrier layer as an intermediate layer, and has an innerlayer and an outer layer made of the thermoplastic resin (B). In thiscase, the ratio (Y2/Y) is preferably at least {fraction (1/100)}, morepreferably at least {fraction (5/100)}.

With regard to the suppression of fuel permeation, it is preferable toblend barrier resin (A) into the thermoplastic resin (B) for the outerlayer. By employing such a configuration, a certain mechanical strengthcan be attained, the thermal fusability with components for fuelcontainers can be improved, and a fuel container with even bettergasoline barrier properties can be obtained. The outer layer can be asingle layer or multiple layer structure, and when it is a multiplelayer structure, then, with regard to the gasoline barrier properties,it is preferable that the thermoplastic resin layer into which thebarrier resin (A) is blended is the outermost layer.

Like in the first fuel container, in the second, third and fourth fuelcontainer too, the occurrence of burr is unavoidable when producing thecontainer especially by blow-molding. As in the first fuel container, itis possible to remelt this burr together with unacceptable pieces ofproducts and use it for a recovered layer.

It is preferable to mount a component for fuel containers on the openingportion provided in the body of the fuel container of the presentinvention. To be specific, suitable component for fuel containersincludes fuel tank connectors, fuel tank caps, and fuel tank valves, butthere is no limitation concerning these.

To sufficiently exhibit the effect of the present invention, it ispreferable that the component for fuel containers has good barrierproperties. Suitable components for fuel containers include componentsmade of metal and components made of a resin composition having goodbarrier properties (Japanese Patent Application Nos. 11-172151 and11-172152).

In a particularly preferable embodiment, the second to fourth fuelcontainer is a coextrusion blow-molded fuel container having an innerlayer and an outer layer made of the thermoplastic resin (B) and abarrier layer, wherein the pinch-off part is covered by a barriermember, and the cutting face of an opening in the body is covered with abarrier member. Even more preferably, a component for fuel containerswith good barrier properties is mounted on this fuel container.

The resulting fuel container has very good fuel barrier properties, sothat it can be used as a fuel container for which particularly highbarrier properties are demanded, such as a gasoline tank for a vehicle.

EXAMPLES

The following is an explanation of the present invention by way ofexamples. It should be understood that the present invention is in noway limited by these examples. The following methods were used for thevarious tests in these examples.

(1) Fuel Permeation Amount at the Pinch-off Part

A film with the structure 60 μm polyethylene/12 μm aluminum foil/60 μmpolyethylene was heat-laminated with a 170° C. heating iron onto thesurface (except for the pinch-off part) of a 500 ml tank obtained bymolding, thereby preventing the permeation of gasoline at all portionsbut the pinch-off part. Then, 400 ml of Ref. fuel C(toluene/isooctane=1/1) was filled as model gasoline into this tank, andthe opening was sealed with a film with the structure 60 μmpolyethylene/12 μm aluminum foil/60 μm polyethylene. The tank wasshelved for three months at 40° C. and 65% RH. This experiment wascarried out on five 500 ml tanks, the change of the weight of the tanksbefore and after the shelf test was determined, and the average valuetaken as the permeation amount through the pinch-off part.

(2) Impact Resistance

A 500 ml tank obtained by molding was filled with 400 ml anti-freezingfluid and shelved for three days at −40° C. Then the tank was droppedonto an iron plate from 1 m height with its pinch-off part facingdownward (n=5). The state of the pinch-off part was evaluated on a scaleof four values, and of the five tanks, the second worst state of thepinch-off part was taken as the evaluation result:

Class A: No deformation at all.

Class B: Slight deformation but no cracks.

Class C. Pinch-off part shows small cracks.

Class D. Pinch-off part shows large cracks.

(3) Deformation of the Tank

It was evaluated visually whether the tank shows deformation.

(4) Evaluation of the fuel or gasoline permeation amount through thematerial used in examples.

(4.1) Evaluation of the Fuel Permeation Amount of the Barrier Resin (A)

A specimen of a layered product including a layer of barrier resin (A)was prepared as explained below, the fuel permeation amount of thislayered product was determined, and converted into the permeation amountof barrier resin of a predetermined thickness.

For the thermoplastic resin (B), the high-density polyethylene (HDPE)BA-46-055 (having a density of 0.970 g/cm³, and a MFR of 0.03 g/10 minat 190° C. and 2160 g) by Paxon was used; for the adhesive resin (D),ADMER GT-6A (having a MFR of 0.94 g/10 min at 190° C. and 2160 g) byMitsui Chemicals, Inc. was used. The barrier resin (A), thethermoplastic resin (B) and the adhesive resin (D) were given intoseparate extruders, and a coextrusion sheet with a total thickness of120 μm having the structure high-density polyethylene/adhesiveresin/barrier resin (A)/adhesive resin/high-density polyethylene (filmthickness 50 μm/5 μm 10 μm/5 μm 50 μm) was obtained by extrusionmolding. In the above coextrusion sheet molding, the high-densitypolyethylene was extruded from an extruder (barrel temperature: 170 to210° C.) having a uniaxial screw of 65 mm diameter and L/D=24, theadhesive resin was extruded from an extruder (barrel temperature: 160 to210° C.) having a uniaxial screw of 40 mm diameter and L/D=22, and thebarrier resin (A) was extruded from an extruder (barrel temperature: 170to 210° C.) having a uniaxial screw of 40 mm diameter and L/D=22 into afeed-block-type die (600 mm width and temperature adjusted to 210° C.)to obtain a coextrusion sheet (a1).

One side of the coextrusion sheet (a1) was covered with aluminumadhesive tape (product by FP Corp., trade name “Alumi-seal”; fuelpermeation amount of 0 g·20 μm/m²·day), thereby obtaining thealuminum-covered sheet (b1).

Both the coextrusion sheet (a1) and the aluminum-covered sheet (b1) werecut into pieces of 210 mm×300 mm size. Then these pieces were folded inthe middle so their size became 210 mm×150 mm, and using the Heat SealerT-230 by Fuji Impulse Co., pouches were prepared by heat-sealing of anytwo sides with dial 6 so that the seal width becomes 10 mm. Thus,pouches (a2) made of the coextrusion sheet only and aluminum-coveredpouches (b2) were obtained. The aluminum-covered pouches (b2) were madeso that the aluminum layer was on the outside.

Then, 200 ml of Ref. fuel C (toluene/isooctane=1/1) was filled as modelgasoline into the pouches through the opening portions, and then thepouches were heat-sealed with a sealing width of 10 mm by theafore-mentioned method.

The pouches, filled with gasoline, were shelved in an explosion-proofthermo-hygrostat chamber (at 40° C. and 65% RH), and the weight of thepouches was measured every seven days over a period of three months.This experiment was carried out on five each of the coextrusion sheetpouches (a2) and the aluminum-covered pouches (b2). The weight of thepouches before and during the shelf-test was measured, and the gasolinepermeation amount (fuel permeation amount) was calculated from the slopeof a curve prepared according to the weight change of the pouches overthe shelf time.

The fuel permeation amount of the pouches (a2) made only of thecoextrusion sheet corresponds to the sum of the permeation amountthrough the pouch surface and through the heat-sealing portions, whereasthe fuel permeation amount of the aluminum-covered pouches (b2)corresponds to the permeation amount through the heat-sealing portions.

{fuel permeation amount through (a2)}—{fuel permeation amount through(b2)} was taken as the fuel permeation amount per 10 μm of the barrierresin (A). Converting this into the permeation amount per 20 μm of abarrier resin (A) layer, the resulting value was taken as the fuelpermeation amount (g·20 μm/m²·day) of the barrier resin (A).

(4.2) Evaluation of the Fuel Permeation Amount of the ThermoplasticResin (B)

Using a Labo-Plast Mill by Toyo Seiki Co. (with 20 mm diameter andL/D=22), extrusion molding was performed at a temperature correspondingto the melting point of the thermoplastic resin plus 20° C. with a coathanger die of 300 mm width, and a sheet of 100 μm thickness wasobtained. This sheet was cut into pieces of 210 mm×300 mm size.

Then these pieces were folded in the middle so their size became 210mm×150 mm, and using the Heat Sealer T-230 by Fuji Impulse Co., poucheswere prepared by heat-sealing of any two sides with dial 6 so that theseal width becomes 10 mm.

Then, 200 ml of Ref. fuel C (toluene/isooctane=1/1) was filled as modelgasoline into the resulting pouches through the opening portions, andthen the pouches were heat-sealed with a sealing width of 10 mm by theaforementioned method.

The pouches, filled with gasoline, were shelved in an explosion-proofthermo-hygrostat chamber (at 40° C. and 65% RH), and the weight of thepouches was measured every six hours over a period of three days. Thisexperiment was carried out on five pouches. The weight of the pouchesbefore and during the shelf-test was measured, and the gasolinepermeation amount (fuel permeation amount) was calculated from the slopeof a curve prepared according to the weight change of the pouches overthe shelf time. By thickness conversion, the permeation amount (g·20μm/m²·day) was calculated.

(4.3) Evaluation of the Fuel Permeation Amount of the Barrier Material(C) (in Case of a Thermoplastic Resin)

The fuel permeation amount was measured using the same method as for thebarrier resin (A).

(4.4) Evaluation of the Fuel Permeation Amount of the Barrier Material(C)(in Case of Pastes and Liquids)

For the thermoplastic resin (B), the aforementioned high-densitypolyethylene (HDPE) BA-46-055 by Paxon was provided, and using theLabo-Plast Mill by Toyo Seiki Co. (with 20 mm diameter and L/D=22),extrusion molding was performed at a temperature according to themelting point of the HDPE plus 20° C. with a coat hanger die of 300 mmwidth, and a sheet of 100 μm thickness was obtained. This sheet was cutinto pieces of 210 mm×300 mm size, and a paste of the barrier materialwas applied to its surface with a Mayer bar so that the barrier materialwas applied at a rate of 5 g/m².

Then, a high-density polyethylene sheet of 100 μm thickness that was thesame as described above was layered onto the surface on which thebarrier material (C) has been applied, thereby producing a two-resinthree-layer sheet.

One side of this multilayered sheet was covered with an aluminumadhesive tape (product by FP Corp., trade name “Alumi-seal”; fuelpermeation amount of 0 g·20 μm/m²·day). Pouches were prepared with themethod explained under 4.1 above using this covered layered sheet, andthe fuel permeation amount of the barrier material (C) was determined.

(4.5) Evaluation of the Fuel Permeation Amount When the Barrier Material(C) is a Metal Foil

The fuel permeation amount was taken to be 0 g·20 μm/m²·day.

(5) Fuel Permeation Amount of the Tank

First, 400 ml liters of Ref., fuel C (toluene/isooctane=1/1) were filledas model gasoline into a blow-molded 500 ml tank through an openingformed by blow-molding, and this opening was sealed with an aluminumadhesive tape (product by FP Corp., trade name “Alumi-seal”; fuelpermeation amount of 0 g·20 μm/m²·day). Then, the tank was shelved at40° C. and 65% RH for three months. This experiment was performed withfive 500 ml tanks, the average change of the weight of the tanks beforeand after the shelf test was determined, and taken as the gasolinepermeation amount of the tank.

Example 1

For the thermoplastic resin (B), the high-density polyethylene (HDPE)BA-46-055 (having a density of 0.970 g/cm³, and a MFR of 0.03 g/10 minat 190° C. and 2160 g) by Paxon was used; for the adhesive resin (D),ADMER GT-6A (having a MFR of 0.94 g/10 min at 190° C. and 2160 g) byMitsui Chemicals, Inc. was used; and for the barrier resin (A), anethylene-vinyl alcohol copolymer including 32 mol % of ethylene andhaving a degree of saponification of 99.5 mol %, and having a MFR of1.3/10 min at 190° C. and 2160 g was used. Using these resins, a fueltank was obtained by blow-molding with a blow-molding machine TB-ST-6Pby Suzuki Tetsukousho according to the following steps. (The molding inthe following examples and comparative examples was performed with thesame blow-molding machine.) A three-resin five-layered parison with thestructure (inner layer) HDPE/Tie/Barrier/Tie/HDPE (outer layer) wasextruded at 210° C. (“HDPE” denotes an high-density polyethylene layer,“Tie” denotes an adhesive layer, and “Barrier” denotes a barrier layer;this is the same in the following examples and comparative examples).Then, molding was performed at a mold-cramping force of 3 tons with amold having a pinch-off part forming section as shown in FIG. 4a.Blowing was performed in the mold at 15° C., such that the ratio (X/Y)of the distance (X) between end portions of the barrier layer and theaverage thickness (Y) of the container body was {fraction (3/1000)}, theratio (H/L) between height and length of the pinch-off part was 0.5, andthe ratio (Y1/Y) between the total thickness (Y1) of the layers of thecontainer body that are located on the inside with respect to thebarrier layer and the average thickness (Y) of the container body was{fraction (48/100)}, and after cooling for 20 sec, a 500 ml tank with atotal layering thickness of 1000 μm ((inner layer)HDPE/The/Barrier/Tie/HDPE (outer layer)=460/20/30/20/470 μm) wasobtained (MFRbarrier/MFRinside=43). The amount of fuel permeatingthrough the pinch-off part of the tank was 0.02 g/3 months, the impactresistance was Class A, and deformation of the tank was not observed.

Table 1 shows the molding conditions (i.e., mold shape for the pinch-offpart forming section, ratio (X/Y) of the distance (X) between endportions of the barrier layer and the average thickness (Y) of thecontainer body, ratio (H/L) between height and length of the pinch-offpart, ratio (Y1/Y) between the total thickness (Y1) of the layers of thecontainer body that are located on the inside with respect to thebarrier layer and the average thickness (Y) of the container body, andmold-cramping force) employed in this example, as well as the evaluationresults (amount of fuel permeating through the pinch-off part, impactresistance, and tank deformation) for the obtained tank.

Example 2 and Comparative Examples 1 and 2

A 500 ml tank was prepared and evaluated with the same procedure as forExample 1, except that a mold having a pinch-off part forming sectionshown in one of FIGS. 4a, 4 b and 4 d (shown in Table 1) was used whileadjusting the mold-cramping force. Table 1 shows the molding conditionsfor this example and the comparative examples as well as the evaluationresults for the obtained tanks.

Comparative Example 3

For the thermoplastic resin (B), the high-density polyethylene (HDPE)J-REX (having a density of 0.970 g/cm³, and a MFR of 0.3 g/10 min at190° C. and 2160 g) by JPO was used; for the adhesive resin (D) and thebarrier resin (A), the same resins as the ones in Example 1 were used.Using these resins, a fuel tank was obtained by blow-molding accordingto the following steps. A three-resin five-layered parison with thestructure (inner layer) HDPE/Tie/Barrier/Tie/HDPE (outer layer) wasextruded at 210° C. Then, molding was performed at a mold-cramping forceof 4 tons with a mold having a pinch-off part forming section as shownin FIG. 4a. Blowing was performed in the mold at 15° C., such that theratio (X/Y) of the distance (X) between end portions of the barrierlayer and the average thickness (Y) of the container body was {fraction(1/20000)}, the ratio (H/L) between height and length of the pinch-offpart was 0.5, and the ratio (Y1/Y) between the total thickness (Y1) ofthe layers of the container body that are located on the inside withrespect to the barrier layer and the average thickness (Y) of thecontainer body was {fraction (45/100)}, and after cooling for 20 sec, a500 ml tank with a total layering thickness of 1000 μm ((inner layer)HDPE/Tie/Barrier/Tie/HDPE (outer layer)=430/20/30/20/500 μm) wasobtained (MFRbarrier/MFRinside=4.3). The amount of fuel permeatingthrough the pinch-off part of the tank was 0.01 g/3 months, the impactresistance was Class D, and deformation of the tank was not observed.

Table 1 shows the molding conditions used for this example, as well asthe evaluation results for the obtained tank.

Comparative Example 4

For the thermoplastic resin (B), the adhesive resin (D) and the barrierresin (A), the same resins as the ones in Example 1 were-used, and afuel tank was obtained by blow-molding according to the following steps.A three-resin five-layered parison with the structure (inner layer)HDPE/Tie/Barrier/Tie/HDPE (outer layer) was extruded at 210° C. Then,molding was performed at a mold-cramping force of 3 tons with a moldhaving a pinch-off part forming section as shown in FIG. 4d. Blowing wasperformed in the mold at 15° C., such that the ratio (X/Y) of thedistance (X) between end portions of the barrier layer and the averagethickness (Y) of the container body was {fraction (3/1000)}, the ratio(H/L) between height and length of the pinch-off part was 0.5, and theratio (Y1/Y) between the total thickness (Y1) of the layers of thecontainer body that are located on the inside with respect to thebarrier layer and the average thickness (Y) of the container body was{fraction (20/100)}, and after cooling for 20 sec, a 500 ml tank with atotal layering thickness of 1000 μm ((inner layer)HDPE/Tie/Barrier/Tie/HDPE (outer layer)=180/20/30/20/750 μm) wasobtained (MFRbarrier/MFRinside=43). The amount of fuel permeatingthrough the pinch-off part of the tank was 0.02 g/3 months, the impactresistance was Class C, and deformation of the tank was not observed.

Table 1 shows the molding conditions used for this example, as well asthe evaluation results for the obtained tank.

Example 3

For the thermoplastic resin (B), the adhesive resin (D) and the barrierresin (A), the same resins as the ones in Example 1 were used. Moreover,as a recovered resin, a resin mixture obtained by crushing a tank madein accordance with Example 1 was used. Using these resins, a fuel tankwas obtained by blow-molding according to the following steps. Afour-resin six-layered parison with the structure (inner layer)HDPE/Tie/Barrier/Tie/recovered layer/HDPE (outer layer) was extruded at210° C. Then, molding was performed at a mold-cramping force of 3 tonswith a mold having a pinch-off part forming section as shown in FIG. 4a.Blowing was performed in the mold at 15° C., such that the ratio (X/Y)of the distance (X) between end portions of the barrier layer and theaverage thickness (Y) of the container body was {fraction (4/1000)}, theratio (H/L) between height and length of the pinch-off part was 0.5, andthe ratio (Y1/Y) between the total thickness (Y1) of the layers of thecontainer body that are located on the inside with respect to thebarrier layer and the average thickness (Y) of the container body was{fraction (49/100)}, and after cooling for 20 sec, a 500 ml tank with atotal layering thickness of 1000 μm ((inner layer)HDPE/Tie/Barrier/Tie/recovered layer/HDPE (outerlayer)=470/20/30/20/200/260 μm) was obtained (MFRbarrier/MFRinside=43).The amount of fuel permeating through the pinch-off part of the tank was0.02 g/3 months, the impact resistance was Class A, and deformation ofthe tank was not observed.

Table 2 shows the molding conditions used for this example, as well asthe evaluation results for the obtained tank.

Example 4 and Comparative Examples 5 and 6

A 500 ml tank was prepared and evaluated with the same procedure as forExample 3, except that a mold having a pinch-off part forming sectionshown in one of FIGS. 4a, 4 c, and 4 d (shown in Table 2) was used whileadjusting the mold-cramping force.

Table 2 shows the molding conditions for this example and thecomparative examples as well as the evaluation results for the obtainedtanks.

Comparative Example 7

For the thermoplastic resin (B), the high-density polyethylene (HDPE)J-REX (having a density of 0.970 g/cm³, and a MFR of 0.3 g/10 min at190° C. and 2160 g) by JPO was used; for the adhesive resin (D) and thebarrier resin (A), the same resins as the ones in Example 1 were used.Moreover, as a recovered resin, a resin mixture obtained by crushing atank made in accordance with Example 1 was used. Using these resins, afuel tank was obtained by blow-molding according to the following steps.A four-resin six-layered parison with the structure (inner layer)HDPE/Tie/Barrier/Tie/recovered layer/HDPE (outer layer) was extruded at210° C. Then, molding was performed at a mold-cramping force of 4 tonswith a mold having a pinch-off part forming section as shown in FIG. 4a.Blowing was performed in the mold at 15° C., such that the ratio (X/Y)of the distance (X) between end portions of the barrier layer and theaverage thickness (Y) of the container body was {fraction (1/30000)},the ratio (H/L) between height and length of the pinch-off part was 0.5,and the ratio (Y1/Y) between the total thickness (Y1) of the layers ofthe container body that are located on the inside with respect to thebarrier layer and the average thickness (Y) of the container body was{fraction (45/100)}, and after cooling for 20 sec, a 500 ml tank with atotal layering thickness of 1000 μm ((inner layer)HDPE/The/Barrier/The/recovered layer/HDPE (outerlayer)=430/20/30/20/200/300 μm) was obtained (MFRbarrier/MFRinside=4.3).The amount of fuel permeating through the pinch-off part of the tank was0.01 g/3 months, the impact resistance was Class D, and deformation ofthe tank was not observed.

Table 2 shows the molding conditions used for this example, as well asthe evaluation results for the obtained tank.

Comparative Example 8

For the thermoplastic resin (B), the adhesive resin (D) and the barrierresin (A), the same resins as the ones in Example 1 were used. Moreover,as a recovered resin, a resin mixture obtained by crushing a tank madein accordance with Example 1 was used. Using these resins, a fuel tankwas obtained by blow-molding according to the following steps. Afour-resin six-layered parison with the structure (inner layer)HDPE/Tie/Barrier/Tie/recovered layer/HDPE (outer layer) was extruded at210° C. Then, molding was performed at a mold-cramping force of 3 tonswith a mold having a pinch-off part forming section as shown in FIG. 4d.Blowing was performed in the mold at 15° C., such that the ratio (X/Y)of the distance (X) between end portions of the barrier layer and theaverage thickness (Y) of the container body was {fraction (3/1000)}, theratio (H/L) between height and length of the pinch-off part was 0.5, andthe ratio (Y1/Y) between the total thickness (Y1) of the layers of thecontainer body that are located on the inside with respect to thebarrier layer and the average thickness (Y) of the container body was{fraction (21/100)}, and after cooling for 20 sec, a 500 ml tank with atotal layering thickness of 1000 μm ((inner layer)HDPE/Tie/Barrier/Tie/recovered layer/HDPE (outerlayer)=190/20/30/20/210/530 μm) was obtained (MFRbarrier/MFRinside=43).The amount of fuel permeating through the pinch-off part of the tank was0.02 g/3 months, the impact resistance was Class D, and deformation ofthe tank was not observed.

Table 2 shows the molding conditions used for this example, as well asthe evaluation results for the obtained tank.

Example 5

For the thermoplastic resin (B), the adhesive resin (D) and the barrierresin (A), the same resins as the ones in Example 1 were used. Moreover,as a recovered resin, a resin mixture obtained by crushing a tank madein accordance with Example 1 was used. Using these resins, a fuel tankwas obtained by blow-molding according to the following steps. Afour-resin seven-layered parison with the structure (inner layer)HDPE/recovered layer/Tie/Barrier/Tie/recovered layer/ HDPE (outer layer)was extruded at 210° C. Then, molding was performed at a mold-crampingforce of 3 tons with a mold having a pinch-off part forming section asshown in FIG. 4a. Blowing was performed in the mold at 15° C., such thatthe ratio (X/Y) of the distance (X) between end portions of the barrierlayer and the average thickness (Y) of the container body was {fraction(4/1000)}, the ratio (H/L) between height and length of the pinch-offpart was 0.5, and the ratio (Y1/Y) between the total thickness (Y1) ofthe layers of the container body that are located on the inside withrespect to the barrier layer and the average thickness (Y) of thecontainer body was {fraction (47/100)}, and after cooling for 20 sec, a500 ml tank with a total layering thickness of 1000 μm ((inner layer)HDPE/recovered layer/Tie/Barrier/Tie/recovered layer/HDPE (outerlayer)=260/190/20/30/20/200/280 μm) was obtained(MFRbarrier/MFRinside=43). The amount of fuel permeating through thepinch-off part of the tank was 0.02 g/3 months, the impact resistancewas Class B, and deformation of the tank was not observed.

Table 3 shows the molding conditions used for this example, as well asthe evaluation results for the obtained tank.

Example 6 and Comparative Examples 9 and 10

A 500 ml tank was prepared and evaluated with the same procedure as forExample 5, except that a mold having a pinch-off part forming sectionshown in one of FIGS. 4a, 4 b, and 4 d (shown in Table 3) was used whileadjusting the mold-cramping force.

Table 3 shows the molding conditions for this example and thecomparative examples as well as the evaluation results for the obtainedtanks.

Comparative Example 11

For the thermoplastic resin (B), the high-density polyethylene (HDPE)J-REX (having a density of 0.970 g/cm, and a MFR of 0.3 g/10 min at 190°C. and 2160 g) by JPO was used; and for the adhesive resin (D) and thebarrier resin (A), the same resins as the ones in Example 1 were used.Moreover, as a recovered resin, a resin mixture obtained by crushing atank made in accordance with Example 1 was used. Using these resins, afuel tank was obtained by blow-molding according to the following steps.A four-resin seven-layered parison with the structure (inner layer)HDPE/recovered layer/Tie/Barrier/Tie/recovered layer/HDPE (outer layer)was extruded at 210° C. Then, molding was performed at a mold-crampingforce of 4 tons with a mold having a pinch-off part forming section asshown in FIG. 4a. Blowing was performed in the mold at 15° C., such thatthe ratio (X/Y) of the distance (X) between end portions of the barrierlayer and the average thickness (Y) of the container body was {fraction(1/30000)}, the ratio (H/L) between height and length of the pinch-offpart was 0.5, and the ratio (Y1/Y) between the total thickness (Y1) ofthe layers of the container body that are located on the inside withrespect to the barrier layer and the average thickness (Y) of thecontainer body was {fraction (44/100)}, and after cooling for 20 sec, a500 ml tank with a total layering thickness of 1000 μm ((inner layer)HDPE/recovered layer/Tie/Barrier/Tie/recovered layer/HDPE (outerlayer)=230/190/20/30/20/220/290 μm) was obtained(MFRbarrier/MFRinside=4.3). The amount of fuel permeating through thepinch-off part of the tank was 0.01 g/3 months, the impact resistancewas Class D, and deformation of the tank was not observed.

Table 3 shows the molding conditions used for this comparative example,as well as the evaluation results for the obtained tank.

Comparative Example 12

For the thermoplastic resin (B), the adhesive resin (D) and the barrierresin (A), the same resins as the ones in Example 1 were used. Moreover,as a recovered resin, a resin mixture obtained by crushing a tank madein accordance with Example 1 was used. Using these resins, a fuel tankwas obtained by blow-molding according to the following steps. Afour-resin seven-layered parison with the structure (inner layer)HDPE/recovered layer/Tie/Barrier/Tie/recovered layer/HDPE (outer layer)was extruded at 210° C. Then, molding was performed at a mold-crampingforce of 3 tons with a mold having a pinch-off part forming section asshown in FIG. 4d. Blowing was performed in the mold at 15° C., such thatthe ratio (X/Y) of the distance (X) between end portions of the barrierlayer and the average thickness (Y) of the container body was {fraction(3/1000)}, the ratio (H/L) between height and length of the pinch-offpart was 0.5, and the ratio (Y1/Y) between the total thickness (Y1) ofthe layers of the container body that are located on the inside withrespect to the barrier layer and the average thickness (Y) of thecontainer body was {fraction (19/100)}, and after cooling for 20 sec, a500 ml tank with a total layering thickness of 1000 μm ((inner layer)HDPE/recovered layer/Tie/Barrier/Tie/recovered layer/HDPE (outerlayer)=100/70/20/30/20/270/490 μm) was obtained(MFRbarrier/MFRinside=43). The amount of fuel permeating through thepinch-off part of the tank was 0.02 g/3 months, the impact resistancewas Class D, and deformation of the tank was not observed.

Table 3 shows the molding conditions used for this example, as well asthe evaluation results for the obtained tank.

TABLE 1 Molding conditions Evaluation of tank Mold Fuel permeationPinch- cramping through pinch-off off force portion Impact DeformationX/Y Y1/Y H/L blade (ton) (g/3 months) resistance of tank Example 13/1000 48/100 0.5 FIG. 4a 3 0.02 A No Example 2 1/200  47/100 1 FIG. 4d2 0.03 A No Comparative 1/6   52/100 1 FIG. 4a 0.8 0.07 B Yes Example 1Comparative 1/6   43/100 4 FIG. 4b 0.8 0.07 C Yes Example 2 Comparative 1/20000 45/100 0.5 FIG. 4a 4 0.01 D No Example 3 Comparative 3/100020/100 0.5 FIG. 4d 3 0.02 C No Example 4

TABLE 2 Molding conditions Evaluation of tank Mold Fuel permeationPinch- cramping through pinch-off off force portion Impact DeformationX/Y Y1/Y H/L blade (ton) (g/3 months) resistance of tank Example 34/1000 49/100 0.5 FIG. 4a 3 0.02 A No Example 4 3/400  48/100 1 FIG. 4d2 0.03 B No Comparative 1/6   53/100 1 FIG. 4a 0.8 0.07 C Yes Example 5Comparative 1/6   44/100 4 FIG. 4c 0.8 0.07 C Yes Example 6 Comparative 1/30000 45/100 0.5 FIG. 4a 4 0.01 D No Example 7 Comparative 3/100021/100 0.5 FIG. 4d 3 0.02 D No Example 8

TABLE 3 Molding conditions Evaluation of tank Mold Fuel permeationPinch- cramping through pinch-off off force portion Impact DeformationX/Y Y1/Y H/L blade (ton) (g/3 months) resistance of tank Example 54/1000 47/100 0.5 FIG. 4a 3 0.02 B No Example 6 3/400  48/100 1 FIG. 4d2 0.03 B No Comparative 1/6   54/100 1 FIG. 4a 0.8 0.07 D Yes Example 9Comparative 1/6   42/100 4 FIG. 4b 0.8 0.07 D Yes Example 10 Comparative 1/30000 44/100 0.5 FIG. 4a 4 0.01 D No Example 11 Comparative 3/100019/100 0.5 FIG. 4d 3 0.02 D No Example 12

The coextrusion blow-molded tanks obtained by Examples 1 to 6, whichhave pinch-off parts with a configuration according to the presentinvention, have good barrier properties, and excellent dart-impactstrength, and have little or no deformation. In Comparative Examples 1and 2, on the other hand, in which the ratio (X/Y) of the distance (X)between end portions of the barrier layer and the average thickness (Y)of the container body exceeds {fraction (1/10)}, the barrier propertiesare unsatisfactory. The impact resistance of the pinch-off parts is low,and deformation can be observed in the resulting tanks. Moreover, inComparative Example 3, in which the ratio (X/Y) is less than {fraction(1/10000)}, the impact resistance of the pinch-off part isextra-ordinarily low. Furthermore, in Comparative Example 4, in whichthe ratio (Y1/Y) between the total thickness (Y1) of the layers of thecontainer body that are located on the inside with respect to thebarrier layer and the average thickness (Y) of the container body isless than {fraction (3/10)}, the impact resistance of the pinch-off partis insufficient.

The present invention can also be advantageously applied to coextrusionblow-molded containers including a recovered layer among their layers.Also when recovered layers are arranged at both sides of the barrierlayer, as for example in Examples 5 and 6 of the present invention, acoextrusion blow-molded container was obtained, in which the barrierproperties are excellent, in which the container has no deformation, andin which the impact resistance of the pinch-off part can be maintainedto a certain degree. On the other hand, in Comparative Examples 9 to 12,in which recovered layers are arranged on both sides of the barrierlayer and which do not have the configuration of the present invention,the impact resistance was in all cases extra-ordinarily poor.

Example 7

For the thermoplastic resin (B), the high-density polyethylene (HDPE)BA-46-055 (having a density of 0.970 g/cm³, a MFR of 0.03 g/10 min at190° C. and 2160 g, and a fuel permeation amount of 4000 g·20 μm/m²·day)by Paxon was used; for the adhesive resin (D), ADMER GT-6A (having a MFRof 0.94 g/10 min at 190° C. and 2160 g) by Mitsui Chemicals, Inc. wasused; and for the barrier resin (A), an ethylene-vinyl alcohol copolymerincluding 32 mol % of ethylene and having a degree of saponification of99.5 mol %, a MFR of 1.3 g/10 min at 190° C. and 2160 g, and a fuelpermeation amount of 0.003 g·20 μm/m²·day was used. Using these resins,a fuel tank was obtained by blow-molding according to the followingsteps. A three-resin five-layered parison with the structure (innerlayer) HDPE/Tie/Barrier/Tie/HDPE (outer layer) was extruded at 210° C.Blowing was performed in the mold at 15° C., and after cooling for 20sec, a 500 ml tank with a total layering thickness of 1000 μm ((innerlayer) HDPE/Tie/Barrier/Tie/HDPE (outer layer)=460/20/30/20/470 μm) wasobtained. The bottom surface diameter of the tank was 100 mm, and thepinch-off part was 100 mm long, 5 mm wide and 1 mm high. The cuttingface of the pinch-off part of the tank was covered with an aluminumadhesive tape (barrier member; product by FP Corp., trade name“Alumi-seal”; fuel permeation amount of 0 g·20 μm/m²·day; this is thesame as for the aluminum adhesive tapes used for the following examplesand comparative examples). In this example, the gasoline permeationamount of the tank was 0.02 g/3 months.

Table 4 shows whether the pinch-off part of the fuel tank obtained inthis example was covered, the value of Y2/Y, and the gasoline permeationamount. Table 4 also shows these results of Examples 8 to 10 andComparative Examples 13 and 14 described below. For the tanks of theseexamples and comparative examples that have an opening, Table 4 alsoshows whether the cutting face of the opening has been covered.

Example 8

A 500 ml tank was manufactured as in Example 7, and an opening of 50 mmdiameter was made in the tank body. The cutting face of this opening inthe tank body was covered with aluminum adhesive tape. Apolyethylene-aluminum layered film of 70 mm diameter with the structure40 μm polyethylene/12 μm aluminum/40 μm polyethylene was heat-laminatedonto the opening portion with a 170° C. heating iron at a sealing widthof 10 mm, so that it covers the opening portion from the outer layer.After the cutting face of the pinch-off part of the tank was coveredwith an aluminum adhesive tape like in Example 7, the gasolinepermeation amount of the tank was measured. In this example, thegasoline permeation amount of the tank was 0.02 g/3 months. Example 9

The preparation of this example was the same as that for Example 8,except that the cutting face of the opening of 50 mm diameter in thetank body was not covered with an aluminum adhesive tape. Then, thegasoline permeation amount of the tank was measured. The measuredpermeation amount of the tank was 0.05 g/3 months.

Example 10

For the thermoplastic resin (B), the adhesive resin (D) and the barrierresin (A), the same resins as the ones in Example 7 were used. Usingthese resins, a fuel tank was obtained by blow-molding according to thefollowing steps. A three-resin five-layered parison with the structure(inner layer) HDPE/Tie/Barrier/Tie/HDPE (outer layer) was extruded at210° C. Blowing was performed in the mold at 15° C., and after coolingfor 20 sec, a 500 ml tank with a total layering thickness of 1000 μm((inner layer) HDPE/Tie/Barrier/Tie/HDPE (outer layer)=800/20/30/20/130μm) was obtained. In this example, the ratio (Y2/Y) of total thickness(Y2) of the layers located on the outside with respect to the barrierlayer and the average thickness (Y) of the container body was {fraction(15/100)}.

After an opening of 50 mm diameter was made in the tank body, the samepolyethylene-aluminum layered film as in Example 8 was heat-laminated onthe opening portion. Moreover, the cutting face of the pinch-off part ofthe tank was covered with an aluminum adhesive tape as in Example 8, andthen the gasoline permeation amount of the tank was measured. Themeasured permeation amount of the tank was 0.03 g/3 months.

Comparative Example 13

The preparation of this example was the same as that for Example 7,except that the cutting face of the pinch-off part was not covered withan aluminum adhesive tape. Then, the gasoline permeation amount of thetank was measured. The measured permeation amount of the tank was 0.04g/3 months.

Comparative Example 14

The preparation of this example was the same as that for Example 8,except that the cutting face of the opening in the tank body and thecutting face of the pinch-off part were not covered with an aluminumadhesive tape. Then, the gasoline permeation amount of the tank wasmeasured. The measured permeation amount of the tank was 0.07 g/3months.

TABLE 4 Cutting face of Fuel Pinch-off aperture permeation amountportion *1 portion *1 Y 2/Y (g/3months) Example 7 ◯ — 49/100 0.02Example 8 ◯ ◯ 49/100 0.02 Example 9 ◯ X 49/100 0.05 Example 10 ◯ X15/100 0.03 Comparative X — 49/100 0.04 Example 13 Comparative X X49/100 0.07 Example 14 *1 ◯ : Covered with aluminum pressure-sensitivetape X : Not covered with aluminum pressure-sensitive tape

In Example 7, in which the container body is not provided with anopening and the cutting face of the pinch-off part is covered with analuminum adhesive tape, the fuel container showed excellent gasolinebarrier properties. In Comparative Example 13, on the other hand, inwhich the cutting face of the pinch-off part is not covered with abarrier member, the fuel permeation amount was 0.04 g/3 months, and thustwice as high as that of Example 7.

Example 8, in which both the cutting face of the pinch-off part and thecutting face of the opening provided in the body of the container arecovered with an aluminum adhesive tape, displayed particularly excellentgasoline barrier properties.

In Examples 9 and 10 the fuel permeation amount is kept low, because thepinch-off part is covered with a barrier member, but the fuel permeationamount is higher than in Example 8, because the cutting face of theopening is not covered. Example 10, in which the value of (Y2/Y) is lessthan {fraction (45/100)}, showed better gasoline barrier properties thanExample 9.

On the other hand, in Comparative Example 14, in which neither thecutting face of the pinch-off part nor the cutting face of the openingprovided in the body of the container are covered with an aluminumadhesive tape, a higher rate of fuel permeation was observed. The fuelpermeation was three times the permeation obtained in Example 8, inwhich both are covered with an aluminum adhesive tape.

Example 11

For the barrier resin (A), EVAL (registered trademark) F101B (EVOHproduced by Kuraray Co., Ltd.; referred to as EVOH(A-1) in thefollowing) was used; for the thermoplastic resin (B), a high-densitypolyethylene (HDPE; HZ8200B by Mitsui Chemicals, Inc.) was used; and forthe adhesive resin (D), maleic anhydride modified LDPE (Admar GT5A byMitsui Chemicals, Inc.) was used, and a 35-liter tank having a 0.85 m²surface area and an EVOH-based multi layered structure with five layersof three resins was prepared with a direct-blow-molding machine. Thelayering structure of this tank was (outer layer) HDPE/adhesiveresin/EVOH (A-1)/adhesive resin/HDPE (inner layer)=2500/100/150/100/2500μm. Then, for the barrier material (C), a mixture (referred to asbarrier material (C-1)) was prepared using the following resins: 30parts by weight of EVOH containing 32 mol % ethylene, and having adegree of saponification of 99.5% and a MFR of 1.6 g/10 min at 190° C.and 2160 g; 15 parts by weight of saponified ethylene-vinyl acetatecopolymer containing 89 mol % ethylene, and having a degree ofsaponification of 97% and a MFR of 5 g/10 min at 190° C. and 2160 g; and55 parts by weight of polyethylene having a density of 0.952 and a MFRof 0.3 g/10 min at 190° C. and 2160 g. These resins were given intobiaxial screw-type vent extruder, and extruding under the presence ofnitrogen at 220° C., pellets were obtained. The fuel permeation amountof the resulting barrier material (C-1) was 45 g·20 μm/m²·day.

The barrier material (C-1) was given into an injection molding machine,and the cylindrical injection-molded article shown in FIG. 11 wasobtained as a barrier member. As shown in FIGS. 11a and 11 b, thismolded article has an outer diameter of 110 mm, an inner diameter of 90mm, a height of 6 mm, and a depth of 2 mm.

The multilayered body of the tank that has been prepared as describedabove was provided with two openings of 70 mm diameter, and grooves withan outer diameter of 110 mm, an inner diameter of 100 m, and a depth of2 mm were provided concentrically around these openings. The grooveportions and the cylindrical barrier member were both heated and for 40sec with a 250° C. iron plate to be softened, and then the peripheralportion of the barrier member was fitted and pressed into the groove.Thus, a multilayered tank with barrier members mounted on its twoopenings was obtained (FIG. 11b shows a cross-sectional view of thevicinity of one of the openings). The fuel permeation of thismultilayered tank was evaluated as follows.

Evaluation of Fuel Permeation

First, 25 liters of Ref. fuel C (toluene/isooctane=1/1), as modelgasoline, were filled into the obtained multilayered tank through anopening formed by blow-molding, and this opening was sealed with analuminum adhesive tape. Then, the tank was put into an explosion-proofthermo-hygrostat chamber (40° C. and 65% RH), and after three months,the weight loss (W) was measured (n=5). This experiment was performedwith five 35-liter tanks, the average change of the weight of the tanksbefore and after the above-mentioned test was determined, and taken asthe gasoline permeation amount of the tank.

For the control tank, a tank was prepared with the same procedure asdescribed above, except that the cutting faces of the openings providedin the tank body were not covered with aluminum adhesive tape. Thiscontrol tank was also put into an explosion-proof thermo-hygrostatchamber (40° C. and 65% RH), and after three months, the weight loss (w)was measured (n=5). The amount of fuel permeating through the outerlayer made of the thermoplastic resin (B) located on the outside withrespect to the barrier layer can be calculated by the followingequation:

 fuel permeation amount (g/3 months)=W−w

In this example, the fuel permeation amount was 0.18 g/3 months.

Example 12

A multilayered tank was prepared with the same procedure as describedfor Example 11, except that the shape of the injection-molded article(i.e., barrier member) made of the barrier material (C-1) was changed tothe shape shown in FIG. 12a, and the depth of the groove provided aroundthe openings of the tank was changed to 4 mm. FIG. 12b shows across-sectional view of the vicinity of one of the openings. Themeasured fuel permeation amount of this multilayered tank was 0.01 g/3months.

Example 13

A multilayered tank including an EVOH barrier layer with 35 litercapacity was prepared with the same procedure as for Example 11, and thebody of the tank was provided with two circular openings of 70 mmdiameter. Then, as shown in FIG. 13a, a portion of the outer layer ofthe tank body was cut away, so as to attain cutouts of 110 mm diameterand 2 mm depth, concentrically around the openings. Disk-shapedinjection-molded articles made of the barrier material (C-1) obtained inExample 11 and having a diameter of 110 mm and 4 mm thickness werefitted into the cutouts as barrier members. Thus, a multilayered tankwith barrier members mounted onto its two opening portions was obtained(see FIG. 13b). The measured fuel permeation amount of this multilayeredtank was 0.10 g/3 months.

Comparative Example 15

A multilayered tank including an EVOH barrier layer with 35 litercapacity was prepared with the same procedure as for Example 11, and thebody of the tank was provided with two circular openings of 70 mmdiameter. Disk-shaped injection-molded articles made of the barriermaterial (C-1) and having a diameter of 110 mm and 4 mm thickness wereobtained. The openings were covered with these barrier members, so thatthe center of the openings coincides with the center of thecorresponding barrier member, the barrier members were thermally fusedto the tank main body, and thus the openings were sealed. Thus, amultilayered tank with barrier members mounted onto its two openingportions was obtained (see FIG. 14). The measured fuel permeation amountof this multilayered tank was 0.42 g/3 months.

The multilayered tanks of Examples 11 to 13, which are configured inaccordance with the present invention, can effectively suppress thepermeation of fuel through the cutting face of an opening, and they haveexcellent gasoline barrier properties. On the other hand, withComparative Example 15, which is not configured in accordance with thepresent invention, satisfactory barrier properties could not beattained.

Thus, the present invention provides a fuel container with high gasolinebarrier properties. The fuel container, in which the pinch-off part hasa specified configuration, has excellent dart-impact strength and haslittle or no deformation. Moreover, excellent gasoline barrierproperties can also be attained when a component for fuel containers ismounted onto opening portions provided in the container body. When thefuel container component has good gasoline barrier properties, then evenhigher gasoline barrier properties can be attained. The fuel containerof the present invention can be used as a gasoline tank for a vehicle.

What is claimed is:
 1. A coextrusion blow-molded fuel container made ofa layered structure comprising: a barrier layer made of a barrier resin(A) and an inner layer located on an inner side of the container withrespect to the barrier layer, the inner layer being made of athermoplastic resin (B) that is different from the barrier resin (A),wherein the container has a pinch-off part formed in a process of blowmolding of a parison made of the layered structure, and wherein thepinch-off part has a cutting face comprising a cutting face of thebarrier layer and a cutting face of the inner layer, and wherein thecutting face of the inner layer is covered by a barrier member made of abarrier material (C) that is the same as or different from the barrierresin (A).
 2. The fuel container of claim 1, further comprising an outerlayer made of a thermoplastic resin that is the same as or differentfrom the thermoplastic resin (B) that is located on an outer side of thecontainer with respect to the barrier layer.
 3. The fuel container ofclaim 1, wherein an adhesive resin layer is located between the barrierlayer and the layer made of the thermoplastic resin (B).
 4. The fuelcontainer of claim 1, wherein a gasoline permeation amount (measured at40° C. and 65% relative humidity) of the barrier resin (A) is at most100 g·20 μm/m²·day.
 5. The fuel container of claim 1, wherein thebarrier resin (A), is at least one selected from the group consisting ofpolyvinyl alcohol resins, polyamides, and aliphatic polyketones.
 6. Thefuel container of claim 1, wherein the thermoplastic resin (B) ishigh-density polyethylene.
 7. The fuel container of claim 1, wherein agasoline permeation amount (measured at 40° C. and 65% relativehumidity) of the barrier material (C) is at most 400 g·20 μm/m²·day. 8.The fuel container of claim 1, wherein the barrier material (C), is atleast one selected from the group consisting of metal foil, epoxy resin,polyvinylidene chloride resin, polyvinylalcohol resin, polyamide resin,polyester resin, and fluorocarbon resin.
 9. The fuel container of claim1, wherein the barrier member covers the cutting face of the inner layervia an adhesive.